"Full-time" and "part-time" are everyday terms, but UK law treats them in a particular way, and there are important rules on maximum working hours and rest. Here is a plain-English guide for England and Wales.
Is there a legal definition of full-time and part-time?
There is no fixed statutory number of hours that makes someone full-time or part-time. In practice:
- full-time usually means around 35–40 hours a week (set by the employer/contract); and
- part-time simply means fewer hours than a comparable full-time worker.
What matters legally is not the label but the protection part-time workers receive.
Part-time workers' rights
Under the Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000, part-time workers must not be treated less favourably than comparable full-time workers because they are part-time (for pay (pro-rata), holiday, benefits, training and opportunities) unless the difference can be objectively justified. So part-timers get the same rights on a pro-rata basis.
Maximum working hours: the 48-hour week
Under the Working Time Regulations 1998, a worker's average working time should not exceed 48 hours a week, usually averaged over a 17-week reference period.
Important: a worker can choose to opt out of the 48-hour limit by agreeing in writing. The opt-out must be voluntary, and the worker can cancel it by giving notice. An employer cannot force a worker to opt out or treat them detrimentally for refusing.
Some workers (e.g. certain transport sectors) have separate rules, and there are special limits for young workers (under 18).
Rest breaks and rest periods
The Working Time Regulations also guarantee minimum rest:
- a 20-minute rest break when the working day is longer than six hours;
- 11 hours' rest between working days (daily rest); and
- at least one day off a week (or two days a fortnight), weekly rest.
Young workers get more generous rest entitlements.
Night work
There are extra protections for night workers, including an average limit of 8 hours' work in 24 and the right to free health assessments.
Practical points for employers
- Treat part-timers equally (pro-rata) to avoid claims under the 2000 Regulations.
- Track working hours to stay within the 48-hour average, and keep signed opt-outs where workers agree to exceed it.
- Provide rest breaks and daily/weekly rest, and assess night workers.
- Be careful with young workers, stricter limits apply.
Key takeaways
- There is no legal hours threshold defining full-time/part-time; full-time is typically ~35–40 hours and part-time is fewer.
- Part-time workers must not be treated less favourably (pro-rata) than comparable full-timers (2000 Regulations).
- The maximum is a 48-hour average week (Working Time Regulations 1998), which a worker can voluntarily opt out of in writing.
- Workers are entitled to rest breaks and daily/weekly rest, with stricter rules for young and night workers.
Sources
- Working Time Regulations 1998 (48-hour average week and opt-out; rest breaks; daily and weekly rest; night work)
- Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000 (equal, pro-rata treatment)
- Separate rules for young workers and certain transport sectors
--- This article is general information about the law of England & Wales as at 2026, not legal advice. For advice on your circumstances, consult a qualified solicitor or HR professional.