Mubarak Marzoon
Founder and editor · Day to Day Tools
I build and maintain every tool on Day to Day Tools, and I write the guides that go with them. I am a software engineer, not a doctor, a dietitian or a regulated financial adviser, and nothing here is personal advice.
What I can do is read the published guidance carefully, get the arithmetic right, and show my working. Every calculator on this site states the formula it uses and where its constants come from, and every article that makes a factual claim links to the source it came from, so you can check it rather than take my word for it.
Where the evidence is genuinely contested, or where a method is far less precise than it looks, I say so in the article instead of rounding it away. Several of the guides here exist mainly to explain why a number people trust is weaker than they think.
What I am and what I am not
I am a software engineer who builds calculators. I am not a doctor, a dietitian, a pharmacist, an accountant or a regulated financial adviser, and I do not pretend to be. Nothing on this site is personal medical or financial advice, and for anything that matters you should speak to someone qualified who knows your circumstances.
What the articles here do is summarise guidance already published by the organisations below, explain the arithmetic behind each tool, and point at the primary source so you can check it. Where the published evidence disagrees with itself, or where a widely trusted number is far less precise than it appears, the article says so rather than picking the tidier answer.
- NHS
- World Health Organization
- Centers for Disease Control and Prevention
- UK Office for National Statistics
- GOV.UK
- MoneyHelper
- peer-reviewed journals indexed on PubMed
Read the full editorial policy for how these are researched, checked and corrected.
All 144 articles
Explainers How Do Fractions and Decimals Convert?
Divide the top by the bottom to get a decimal. Going back means using place value and simplifying. Why some fractions repeat forever and which ones to memorise.
Explainers How Do Roman Numerals Work?
Seven letters, added together, with a smaller letter before a larger one meaning subtract. The rules, the common mistakes, and why clocks often show IIII instead of.
Converters How Do Shoe Sizes Work Across Countries?
UK, US, EU and Japanese sizes use different scales and different starting points. What each measures, why the conversions disagree, and the one measurement that alwa.
Money How Do Student Loan Repayments Work?
You repay a percentage of income above a threshold, not a fixed instalment, and the balance is written off after a set period.
Money How Does VAT Work?
VAT is charged at each stage of production and reclaimed by businesses, so only the final consumer pays it. Why 20 percent added is not 20 percent removed.
Work How Long Is a Notice Period?
Statutory notice is one week after a month of service, rising to one week per year after two years. Contracts usually say more.
Work How Much Does a Meeting Actually Cost?
Multiply attendees by their hourly cost by the duration. A one-hour meeting with eight mid-level staff costs a few hundred pounds.
Work How Much Redundancy Pay Am I Entitled To?
Statutory redundancy pay depends on age, length of service and weekly pay, capped in all three. How the formula works, what it excludes, and when contractual terms b.
Cooking How Much Rice Per Person?
Sixty to 75 grams of dry rice per person as a side, 100 as a main. Rice roughly triples in weight when cooked, which is why the cooked figure looks so different.
Health How Much Salt Should I Eat a Day?
The UK limit is 6 grams, about a teaspoon, and most adults exceed it. Three quarters comes from processed food, not the salt cellar. How to find it and cut it.
Health How Much Vitamin D Do I Need?
UK guidance is 10 micrograms a day, and a supplement is advised for everyone in autumn and winter because sunlight is too weak to make any.
Work How Do I Read a Payslip?
Gross pay at the top, deductions in the middle, net pay at the bottom. What each line means, which codes matter, and the two errors worth checking every month.
Home Is a Smart Meter Worth It?
A smart meter ends estimated bills and shows usage in near real time. It does not reduce your energy use by itself.
Cooking Is an Air Fryer Cheaper Than an Oven?
For one or two portions, yes, by a wide margin. An air fryer heats a small space quickly; an oven heats a large one slowly. Where the saving disappears.
Health What Do Blood Pressure Numbers Mean?
The top number is the pressure when the heart beats, the bottom when it rests. What counts as normal, what raises a reading falsely, and when the numbers matter.
Explainers What Is a Hex Colour Code?
Six characters encoding red, green and blue as three pairs of hexadecimal digits. How to read one at a glance, what the shorthand means, and where the eighth charact.
Work What Is a Probation Period and What Are My Rights?
Probation is a contractual trial period, not a legal status. Your statutory rights apply from day one. What actually changes, and what employers cannot do.
Writing What Is a Regular Expression?
A regex is a pattern that matches text: find every email address, every date, every duplicated word. The syntax that covers most real uses, and where it goes wrong.
Work What Is a Tax Code and How Do I Know If Mine Is Right?
A tax code tells your employer how much you can earn tax-free. 1257L is standard. What the letters mean, which codes signal a problem, and how to get one corrected.
Money What Is an ISA and Which One Do I Need?
An ISA is a wrapper that shelters savings or investments from tax. Four main types, one annual allowance between them, and a straightforward way to pick.
Money What Is National Insurance Actually For?
National Insurance buys entitlement to the State Pension and certain benefits, based on a contribution record rather than the amount paid.
Explainers What Is Standard Deviation?
Standard deviation measures how spread out numbers are around their mean. Small means clustered, large means scattered.
Work What Is Statutory Sick Pay and Who Gets It?
SSP is a fixed weekly amount paid for up to 28 weeks, starting from the fourth day off. Who qualifies, what it pays, and how contractual sick pay differs.
Health What Is the 20-20-20 Rule for Eye Strain?
Every 20 minutes, look at something 20 feet away for 20 seconds. Why screen fatigue is mostly about focus distance and blinking, and what else actually helps.
Explainers What Is the Difference Between JPEG, PNG and WebP?
JPEG for photographs, PNG for graphics and transparency, WebP for both at smaller sizes. Which to use where, and why saving a JPEG twice degrades it.
Explainers What Is the Mean, Median and Mode?
Three ways to describe the middle of a set of numbers, and they can disagree wildly. Which to use, how outliers break the mean, and why the median is usually safer.
Health What SPF Do I Actually Need?
SPF 30 blocks about 97 percent of UVB and SPF 50 about 98. The bigger issue is that most people apply a third of the amount the rating assumes.
Home What Temperature Should I Wash Clothes At?
Thirty degrees suits most everyday laundry and uses far less energy than 60. When a hot wash is genuinely needed, and why the detergent matters more than the dial.
Home What Temperature Should My Fridge Be?
Between 0 and 5 degrees Celsius, with the freezer at minus 18. Why the dial number is not the temperature, where the cold spots are, and how to check with a thermome.
Writing When Should I Use Title Case?
Title case capitalises the important words and leaves short ones lowercase. Which style guide says what, where sentence case is preferred, and the rules that actuall.
Money Does the 50/30/20 Budget Rule Actually Work?
Fifty percent on needs, thirty on wants, twenty on savings. It is memorable and it is wrong for a lot of people. Here is when it fits and how to adjust it.
Explainers How Big Is a Megabyte vs a Gigabyte?
A gigabyte is a thousand megabytes, which is a thousand kilobytes. What each holds in photos, songs and video, and why your 1 TB drive shows as 931 GB.
Explainers How Long Is a Billion Seconds?
A billion seconds is about 31.7 years. A million seconds is 11.6 days. The gap between the two is the clearest illustration there is of how badly we picture large nu.
Health How Long Does It Take to Lose a Pound of Fat?
A pound of body fat holds roughly 3,500 calories. At a 500-calorie daily deficit that is a week, in theory. In practice it slows down, and here is why the maths drifts.
Health How Many Calories Does Sleep Burn?
Roughly 45 to 60 calories an hour for most adults, or 350 to 500 over a night. It is not exercise, but it is a reminder that resting metabolism is most of what you burn each day.
Work How Many Hours Is Part-Time?
There is no legal definition. Part-time means fewer hours than your employer's full-time staff, usually anything under 35 to 37.5 a week.
Cooking How Many Grams Is a Tablespoon?
A tablespoon is 15 ml, but grams depend on what is in it: 15 g of water, 13 g of oil, about 8 g of flour, 12 g of sugar. Why volume to weight is ingredient-specific, with a table.
Health How Many Steps a Day Do I Really Need?
Ten thousand steps came from a 1960s pedometer marketing campaign. Research puts the health benefit at roughly 7,000 to 8,000, with most of the gain in the first few thousand.
Work How Many Working Days Are in a Year?
A standard year has 260 weekdays, or 261 in some leap years. Subtract eight bank holidays and typical annual leave and the number of days actually worked is around 2.
Health How Much Caffeine Is in a Cup of Tea vs Coffee?
A mug of tea has about 47 mg of caffeine, a mug of filter coffee around 140 mg, and an espresso about 65 mg. Brewing time and size change all of these more than people expect.
Money How Much Do I Need to Retire?
Most estimates land between 20 and 25 times your annual spending in retirement, before the State Pension. Here is how the multiple works and what changes it.
Money How Much Does a Car Really Cost Per Year?
Fuel is the cost people track and usually not the largest one. Depreciation, insurance, servicing, tax and parking put most cars at several thousand a year.
Home How Much Does a Shower Cost?
An eight-minute shower costs roughly 30 to 60p in energy and water on a typical tariff, depending on the heater type.
Home How Much Does It Cost to Leave a Light On All Night?
An LED bulb left on for eight hours costs about 2p. An old incandescent costs around 12p. The habit that matters is not the landing light, it is the heating and the appliances.
Home How Much Does It Cost to Run a Tumble Dryer?
A vented or condenser dryer uses 2 to 4 kWh per load, roughly 50p to a pound at current unit rates. Heat pump models use about a third of that. The arithmetic and the alternatives.
Money How Much of My Income Should Go on Rent?
The 30 percent rule is seventy years old and assumed cheaper housing. Here is what the rule actually meant, what people pay now, and a better way to set your ceiling.
Health How Much Protein Do I Need a Day?
The baseline is about 0.75 grams per kilogram of body weight, and most people already exceed it. Training, ageing and weight loss raise the useful amount. What the numbers mean.
Money How Much Should I Have Saved by 30?
The common rule is one year's salary by 30, and most people are nowhere near it. Here is where the rule comes from, why it misleads, and a target that actually helps.
Health How Much Sleep Do Adults Need by Age?
Seven to nine hours for most adults, seven to eight after 65. The need does not fall much with age, but the ability to get it does. What the guidance says and why.
Health How Much Water Should I Actually Drink a Day?
The eight glasses rule has no clear source. UK guidance is six to eight cups of any fluid, food included. Here is what the number means and when to drink more.
Explainers How Do I Compress a Photo for Email?
A phone photo is 3 to 6 MB, and most mailboxes cap attachments at 20 to 25 MB. Resize to 1,600 pixels wide and save at 80 percent JPEG quality for a file under 500 K.
Cooking How Do I Convert Oven Temperatures Between Fan, Gas and Conventional?
Fan ovens run about 20°C lower than conventional for the same result. Gas marks map to fixed temperatures. A quick table and the reasons the conversions are approximate.
Money How Do You Split Bills Fairly When You Earn Different Amounts?
Splitting 50/50 is simple and, on unequal incomes, quietly unfair. Proportional splitting matches contributions to earnings. Here is how, and where it gets complicated.
Explainers How Do I Take a Screenshot on Any Device?
Windows, Mac, iPhone, Android and Chromebook each use a different shortcut. All of them in one place, plus how to capture part of the screen and where the file ends.
Security How Do I Tell If an Email Is a Scam?
Urgency, a mismatched sender address, a link to a site that is not quite the real one, and a request for a payment or a password.
Home How Do I Work Out the Square Metres of a Room?
Multiply length by width in metres for a rectangle. For L-shapes and alcoves, split the room into rectangles and add them. What to measure and how much extra to order.
Money Is Buying in Bulk Actually Cheaper?
Bulk buying saves money on things you use at a steady rate and lose money on things that expire, spoil or stop appealing. The unit price tells you which is which.
Home Which Is Cheaper, Gas or Electric Cooking?
Gas is cheaper per unit of energy but wastes more of it as heat around the pan. Induction is the most efficient electric option. Here is what the numbers say per meal and per year.
Health Is It Bad to Eat Late at Night?
Calories at 10pm are not more fattening than calories at 6pm, but late eating changes sleep, appetite and what people choose. What the evidence actually shows.
Health Is Walking Enough Exercise?
Brisk walking meets the aerobic half of the adult activity guideline entirely. It does not cover strength, which the guideline also asks for. What walking does and what it misses.
Money Is It Better to Pay Off a Mortgage Early or Invest?
Overpaying a mortgage is a guaranteed return equal to your interest rate. Investing usually earns more but is not guaranteed. Here is how to decide on your numbers.
Money Should I Use a 0% Balance Transfer Card?
A 0% balance transfer can save hundreds in interest, or make things worse. It works if you clear the balance inside the window and stop using the old card.
Money What Does APR Actually Mean?
APR is the yearly cost of borrowing including fees, built so loans can be compared. What it includes, what it leaves out, and why the representative rate is not yours.
Security What Does Incognito Mode Actually Hide?
Private browsing stops your browser saving history, cookies and form data on that device. It does not hide you from websites, your employer, your internet provider o.
Money What Is a Good Credit Utilisation Ratio?
Utilisation is the share of your available credit you are using, and it moves your score fast. Under 30 percent is the usual advice; under 10 is better. Here is why.
Health What Is a Healthy Waist Size?
Waist measurement predicts health risk better than BMI for many people. The thresholds are 94 cm for men and 80 cm for women, with higher-risk cut-offs above that.
Health What Is a Normal Resting Heart Rate?
Sixty to one hundred beats per minute is the standard range for adults, and a fit person is often below it. Here is how to measure it properly and when to ask about it.
Security What Is a Passkey and Should I Use One?
A passkey replaces a password with a cryptographic key stored on your device and unlocked by your fingerprint, face or PIN. It cannot be phished or reused.
Work What Is a Pro Rata Salary?
Pro rata means in proportion. A job advertised at 30,000 pro rata for three days a week pays 18,000. How to work it out from hours or days, and what else scales with.
Security What Is a QR Code and Are They Safe to Scan?
A QR code is just a web address or text encoded as a pattern. Scanning is harmless; following the link is where the risk lives.
Health What Is a Standard Drink?
A standard drink is a fixed amount of pure alcohol, and the amount differs by country: 8 g in the UK, 10 g in Australia, 14 g in the US.
Security What Is a VPN and Do I Need One?
A VPN encrypts traffic between your device and a server run by the VPN provider. It hides activity from the local network and shifts trust to the provider.
Money What Is Compound Interest, Explained Simply?
Compound interest is interest earned on interest, and over long periods it dominates everything else. A plain explanation with numbers, and why it cuts both ways.
Work What Is Time and a Half?
Time and a half means being paid 1.5 times your normal hourly rate, usually for overtime, weekends or bank holidays.
Security What Is Two-Factor Authentication and Should I Use It?
Two-factor authentication adds a second check, usually a code from your phone, so a stolen password alone is not enough. It blocks most account takeovers.
Home What Size Rug Do I Need?
The most common rug mistake is buying one too small. For a living room, all front legs of the seating go on the rug; for a bedroom, the rug extends 60 cm beyond the.
Work What Is UTC and Why Does It Matter?
Coordinated Universal Time is the reference every time zone is defined against. It never changes for daylight saving, which is why it appears in flight times, server.
Work When Is the Best Time to Send an Email?
Mid-morning on a Tuesday to Thursday gets the best open rates in most studies, but the honest answer depends on the recipient's time zone, inbox and whether you need.
Health Why Do I Keep Waking Up at 3am?
Waking in the small hours is common and usually explained by sleep architecture, alcohol, stress hormones or a full bladder, not anything sinister. What causes it and what helps.
Explainers Why Is My Phone Storage Full?
Photos and videos are usually the answer, followed by messaging app caches and unused apps. How to find what is taking the space and free most of it without deleting.
Web www or No www? Pick One, Redirect the Rest
The choice barely matters. Serving both does. Here is why Search Console reporting your other domain as a redirect is the sign it is working, not a fault.
Web Design for the Smallest Size It Will Ever Be Seen At
Favicons, app icons, thumbnails and logos in a footer all fail the same way: they were designed large and shrunk. The fix is to reverse the process.
Health When to Stop Drinking Coffee, According to Its Half-Life
Half of a 4pm coffee is still in your system at 9pm. A controlled trial found caffeine six hours before bed cut sleep by over an hour, and nobody noticed.
Web Your Favicon Is 16 Pixels Wide. Design For That.
Most favicons are a shrunken logo, which turns to grey mush in a tab. The fix is one bold shape, two colours, and a filled background.
Money How Big Should Your Emergency Fund Actually Be?
Three to six months of essential spending, not total spending. Getting that distinction right often cuts the target by a third and makes it a goal you finish.
Health How Many Units Is That Drink? The Answer Has Changed
A large glass of wine is 3.25 units and a bottle is under ten. Wine has gained two percentage points of strength in thirty years, and glasses have grown.
Home How Much Concrete Do I Need? And Why It Is Heavier Than You Think
A cubic metre of concrete is 108 bags of 20 kg and weighs 2.4 tonnes. Working that out before ordering changes most people's plan for the weekend.
Health How Tall Will My Child Be? What the Prediction Can and Cannot Tell You
The mid-parental method is what paediatricians use, and it is accurate to within about 10 cm either way. That is a 20 cm window, which is the honest answer.
Money How to Write an Invoice That Actually Gets Paid
Most late payments are not disputes. They are invoices missing a number, sent to the wrong inbox, or with terms nobody bothered to convert into a date.
Writing The Fastest Way to Proofread Is to Stop Reading
Reading silently, your brain repairs the text as it goes. Hearing it removes the shortcut, and several classes of error become impossible to miss.
Money Save or Pay Off Debt First? The Sequence That Actually Works
Neither pure answer survives contact with real life. The order that does starts with a one-month buffer, and skipping it is why most debt plans fail.
Home Stair Rise and Run: Getting the Geometry Right First Time
Divide the height by a whole number of steps and accept the awkward decimal. Rounding the rise and absorbing the error in the last step is a genuine trip hazard.
Money What Should I Charge? Working Out a Freelance Rate That Holds
Dividing your old salary by 2,000 lands 60% to 100% too low. The number that matters is billable hours, and most freelancers bill barely half their time.
Money What Your Employer Actually Paid to Employ You
An employee on 40,000 typically costs 55,000 to 65,000. Knowing the gap matters whether you are going freelance or negotiating a raise.
Money The 700 Hours a Year You Work and Cannot Invoice
Most freelancers bill barely half their working time. Understanding where the rest goes is the difference between a rate that works and one that quietly does not.
Writing Why You Cannot See Your Own Typos
Reading is prediction, not perception. Your brain supplies what should be there, which is exactly why proofreading your own work fails and what to do instead.
Health Exercise Is Excellent for You and a Weak Way to Lose Weight
A 30 minute run burns about what is in one chocolate bar, and appetite claws back much of it. Here is what exercise is actually good for.
Explainers How Anagram Solvers Work Without Checking Every Permutation
Twelve letters have 479 million arrangements. A good solver never generates a single one, and the trick behind it is worth knowing.
Productivity Why Counting in Days Changes What You Do About a Deadline
Ninety days and three months are the same interval, and people act on them differently. The research on temporal framing is unusually practical.
Explainers Learning Morse Code: Why the Chart Is the Wrong Place to Start
Almost everyone learns Morse from a table of dots and dashes and hits a hard ceiling. Here is why, and what the two methods that work do instead.
Productivity The Pomodoro Technique: Which Parts Actually Work
Twenty five minutes is arbitrary. The fixed interval, the enforced breaks and the interruption log are the parts doing the work, and one is usually skipped.
Money Price Is Not Cost: Working Out What Things Actually Cost You
The expensive coat is often the cheap one. Cost per use, total cost of ownership and the honest-use problem, in one place.
Money The Rule of 72: The Only Compound Interest Maths You Need in Your Head
Divide 72 by a rate and you get the doubling time. It works for savings, debt, inflation and fees, and it is accurate to within a few percent.
Explainers The Longest Word Is Usually the Wrong Move
Word game skill is mostly rack management, two-letter words and board awareness. The big play is the part beginners focus on and experts often decline.
Explainers Why Computers Count in Binary and Programmers Count in Hex
Base 10 is a biological accident. Base 2 is a physical one. Here is why hexadecimal sits between them, and why 255 keeps appearing everywhere.
Health Why Your Watch Overestimates How Many Calories You Burned
Validation studies find consumer wearables off by 20% to 90% on energy expenditure, almost always too high. Here is what they measure and what they guess.
Productivity Working Days vs Calendar Days: Why Deadlines Are Closer Than They Look
Six weeks sounds like plenty. It is thirty working days, and probably fewer than twenty once holidays and existing commitments are counted.
Money Debt Snowball vs Avalanche: Which One Should You Actually Use?
The avalanche method always costs less in interest. The snowball method gets finished more often. Here is how to work out which difference matters more for you.
Money How Many Years Before Buying Beats Renting?
The break-even horizon is the number that decides it, and it is far more sensitive to assumptions than most people expect. Here is what moves it.
Money Is Your Pay Rise Actually a Pay Rise?
If prices rose 4% and your salary rose 2%, you took a pay cut. Here is how to work out the number you actually need before a salary review.
Money Rent vs Buy: The Costs Almost Everyone Leaves Out
Comparing a mortgage payment against rent misses about half the cost of owning. Here is the full list, and why the deposit is the biggest omission of all.
Money The Minimum Payment Trap: Why Card Balances Never Move
A 3,000 balance at 22% paid at the minimum takes over twenty years and costs more in interest than you borrowed. Here is exactly how the mechanism works.
Money What Inflation Quietly Does to Money Sitting in a Savings Account
A balance that never goes down can still lose a fifth of its value in a decade. Here is how to see the loss that no statement ever shows you.
Health When Do You Actually Ovulate? Counting Backwards, Not Forwards
Ovulation happens about 14 days before your next period, not 14 days after the last one. That distinction changes the answer for most cycle lengths.
Health Can You Actually Catch Up on Sleep?
Partly, and not the way most people try. A weekend lie-in repays some acute deficit while creating a circadian problem that makes Monday worse.
Home How Much Wallpaper You Actually Need
Pattern repeat, not room size, is what decides the answer. A 64 cm repeat can add a third to the rolls for the same four walls.
Guides How to Read Something Out Loud So It Is Heard Correctly
B, D, E, P, T and V are indistinguishable over a bad line. The NATO alphabet exists because that costs real money and real time.
Money The Pricing Mistake That Quietly Costs Small Businesses Thousands
Markup and margin are not the same number, and confusing them means underpricing every single sale by several percentage points, forever.
Guides How to Measure a Ring Size Without Asking
Fingers change size by up to half a size through the day. Measure in the evening, from a ring that fits, and size up for a wide band.
Home Scaling a Recipe Without Ruining It
Most ingredients double cleanly. Leavening, salt and cooking time do not, and getting those three wrong is why doubled cakes sink and doubled curries are inedible.
Money How to Settle Up After a Group Trip Without Falling Out
The arithmetic is simple. The arguments come from splitting things evenly that were not shared evenly, and from leaving it too long.
Money The Expensive Thing Is Often the Cheap One
Price is what you pay once. Cost is what you pay per use. The two frequently point in opposite directions, and only one of them matters.
Money What Overtime Is Actually Worth
The multiplier applies to the whole hour, entitlement depends on your contract rather than staying late, and it is not taxed at a special rate.
Money Why a 30% Return Might Be a Bad One
A total return without a time period is close to meaningless. The same 30% is excellent over a year and below inflation over ten.
Guides Why Your Broadband Is Slower Than You Paid For
Most of the gap is one unit conversion. Connections are sold in megabits and files are measured in megabytes, and there are eight bits in a byte.
Health You Probably Should Not Test Your One Rep Max
A true max attempt is high risk, disruptive and rarely necessary. An estimate from a hard set of five is safer and good enough for programming.
Security How to Redact Something So It Stays Redacted
Black boxes in PDFs and documents are famously recoverable. Pixelated text has been brute-forced. Here's what actually removes information.
Health Why Most People Train in the Wrong Zone
Zone 3 feels productive and builds neither endurance nor speed. The 80/20 pattern, why 220-minus-age is weak, and what each zone is actually for.
Home Which Appliances Actually Cost You Money
Unplugging chargers saves about £2 a year. The tumble dryer costs £130. Here's where household electricity actually goes, with the arithmetic.
Security What Your Browser Tells Every Site You Visit
Fingerprinting identifies you without cookies, survives private browsing, and can't be cleared. Here's what's exposed, and why hardening often backfires.
Security What Your Photos Give Away When You Share Them
Every phone photo can carry the exact coordinates where it was taken. Here's what's inside the file, who strips it, and how to check before you post.
Guides How to Write So People Actually Read It
Long sentences are the single biggest cause of unreadable writing. Here's what readability scores measure, what they miss, and the five fixes that work.
Home Why Your Baking Goes Wrong: Cups Aren't a Measurement
A cup of flour can weigh 120 g or 150 g depending purely on how it got into the cup. That 25% swing is why recipes fail. And why grams win.
Home How Much Paint Do I Actually Need?
The arithmetic takes thirty seconds, tin coverage figures are optimistic, and the second coat is not negotiable. A guide to buying paint once.
Money How to Actually Save For Something
Saving what's left at the end of the month means saving nothing. Work backwards from the goal, automate the transfer, and check the four honest levers.
Guides What You Actually Need On the Final Exam
The formula takes ten seconds, tells you where your effort is worth most, and is honest when a grade has become arithmetically out of reach.
Money How to Spot a Discount That Isn't One
Stacked discounts don't add up, 'up to 70% off' means almost nothing, and the bigger pack isn't always cheaper. The arithmetic behind retail pricing.
Money What Your Salary Actually Works Out To Per Hour
The 2,080-hour rule, why the hours you really work change the answer, and how to compare a contract rate to a salary without fooling yourself.
Guides How to Schedule Across Time Zones Without Getting It Wrong
Why the offset you memorised is wrong for three weeks a year, which abbreviations are genuinely ambiguous, and how to write a time nobody can misread.
Health Why 6 Hours of Sleep Can Beat 7
Sleep runs in roughly 90-minute cycles. Waking at the end of one instead of the middle explains why you sometimes sleep longer and feel worse.
Security How to Choose a Password That Actually Holds Up
Most password advice is twenty years out of date and made things worse. Here's what genuinely protects an account, in the order that matters.
Health BMI: What the Number Means and What It Definitely Doesn't
BMI was invented in the 1830s to describe populations, not people. Here's what it's genuinely useful for, where it fails, and what to measure instead.
Money What a Loan Actually Costs (And Why the Monthly Payment Hides It)
Lenders quote the monthly payment because it's the smallest number they can show you. Here's how to see the real cost of borrowing before you sign.
Everyday Maths How to Calculate Percentages Without Reaching for a Calculator
The four percentage questions that cover almost every real situation, the mental shortcuts that make them fast, and the three mistakes that cost people money.