How Many Hours Is Part-Time?

People expect a number and there is not one. Part-time is defined by comparison, not by a threshold, and that is a more useful definition than it sounds once you know what follows from it.

The definition

A part-time worker is someone who works fewer hours than a comparable full-time worker at the same employer. That is the whole legal definition. If full-time in your workplace is 37.5 hours, then 30 is part-time. If full-time is 40, then 35 is part-time.

In practice, full-time in the UK clusters between 35 and 40 hours, so part-time is anything meaningfully below that, and most part-time roles fall between 16 and 30 hours.

Thresholds that do exist

While employment law has no cut-off, other systems do, and they cause the confusion:

• 16 hours is a threshold in several benefit and tax credit rules.
• 30 hours is another, used for some working-age benefits and for free childcare entitlement in England.
• Employers often set their own boundaries for benefits eligibility, though these must not discriminate against part-timers.

None of these define part-time. They define who qualifies for particular schemes.

Rights are the same

The Part-time Workers Regulations require that part-time staff are treated no less favourably than full-time colleagues doing similar work. That means:

• The same hourly rate of pay
• The same access to pension schemes
• The same access to training and promotion
• The same sick pay and parental leave arrangements, pro rata
• Overtime rates once the full-time threshold is passed, not before

Any difference has to be objectively justified, and “they are only part-time” is not a justification.

Pro rata

Pay and benefits are scaled to hours. Someone on 3 days a week where full-time is 5 gets 60 percent of the full-time salary and 60 percent of the holiday entitlement.

Holiday is where the arithmetic bites. Full-time statutory leave is 28 days. Three days a week gives 3/5 of 28, which is 16.8 days, rounded up to 17. Working two long days of 9 hours each is 18 hours a week; leave in hours is 18 × 5.6 = 100.8 hours. For irregular patterns, calculating in hours avoids most of the disputes.

Bank holidays are included in the 28-day figure, which catches people out: a part-timer who never works Mondays does not lose out, because their pro rata entitlement includes a share of the bank holidays that fall on Mondays, taken as leave on other days.

What part-time does not change

Your employment status, your continuity of service, your protection against unfair dismissal, your redundancy rights. A part-time employee with five years’ service has the same protections as a full-time one with five years’ service.

The practical question

If you are negotiating a reduction in hours, get the new hours, the pro rata salary and the pro rata holiday in writing, and check that the hourly rate has not quietly changed. It should be identical to the full-time rate. If it is not, ask why.