Unit Converter
Length, weight, temperature, volume, area, speed, data and time — converting live as you type.
Runs entirely in your browser. Nothing you type here is uploaded, stored or logged.
Conversions worth memorising
- 1 inch = 2.54 cm exactly — every imperial length conversion derives from this.
- 1 mile ≈ 1.61 km, and the reverse: multiply km by 0.62.
- 1 kg ≈ 2.2 lb — good enough for luggage limits and gym plates.
- 1 litre ≈ 1.76 UK pints ≈ 2.11 US pints.
- 100 km/h ≈ 62 mph, the conversion that matters at European border crossings.
- °C to °F: double and add 30 for a mental estimate.
The Fibonacci trick for miles and kilometres
Consecutive Fibonacci numbers approximate the mile-to-kilometre ratio, because the golden ratio (1.618) is remarkably close to 1.609. So 3 miles ≈ 5 km, 5 miles ≈ 8 km, 8 miles ≈ 13 km, 13 miles ≈ 21 km. Runners find this genuinely useful — a half marathon is 13.1 miles, or about 21 km.
Where imperial and US customary diverge
They agree on length and weight but not on volume. A US pint is 473 ml; an imperial pint is 568 ml. A US fluid ounce is 29.57 ml; an imperial fluid ounce is 28.41 ml — confusingly, the US ounce is bigger while the US pint is smaller, because a US pint is 16 fl oz and an imperial pint is 20.
The practical consequence: American recipes scaled with a UK measuring jug come out roughly 20% short on liquids. This converter distinguishes the two throughout.
Why temperature is different
Every other conversion here is a straight multiplication, because the scales share a zero point. Temperature scales do not — 0°C and 0°F are different temperatures — so the conversion needs both a multiplier and an offset. That is also why you cannot convert a temperature difference the same way: a rise of 10°C is a rise of 18°F, not 50°F.
Frequently asked questions
How do I convert Celsius to Fahrenheit in my head?
Double it and add 30. It is not exact, but it is within a couple of degrees across normal weather: 20°C → 70 (really 68), 30°C → 90 (really 86). The exact formula is °F = °C × 9/5 + 32.
Why do US and UK gallons differ?
Because they were standardised separately. A US liquid gallon is 3.785 litres; an imperial gallon is 4.546 litres — about 20% larger. The same applies to pints and fluid ounces, which is why American and British recipes are not interchangeable by volume.
What is the difference between mass and weight here?
Strictly, kilograms measure mass and pounds-force measure weight. In everyday use both are treated as mass and converted directly, which is what this tool does and what every kitchen scale and airline luggage limit assumes.
Are digital storage units powers of 1000 or 1024?
Both exist. This converter uses the decimal SI definition (1 MB = 1,000,000 bytes), which is what storage manufacturers and network speeds use. Operating systems often report the binary values (1 MiB = 1,048,576 bytes), which is why a “1 TB” drive shows as roughly 931 GB in Windows.