Pro Rata Salary Explained: Formula, Examples and Part-Time Tax

The pro rata salary formula

Pro rata salary = full-time salary x (your contracted hours ÷ full-time hours).

You can use days instead of hours if each day is the same length: full-time salary x (your days ÷ full-time days). Always check what the employer counts as full time; 35, 37.5 and 40 hours are all common, and the answer changes with it.

Worked examples

3 days a week: a £32,000 role, 3 days out of 5. £32,000 x 3/5 = £19,200 a year, or £1,600 a month gross.

Hours-based: a £28,000 role where full time is 37.5 hours and you work 25. £28,000 x 25/37.5 = £18,666.67.

Hourly equivalent: £32,000 ÷ (37.5 x 52) = £16.41 an hour. Multiply by your weekly hours and 52 to cross-check.

Part-year: a £36,000 full-time job starting on 1 January in a year running to 31 March earns £36,000 x 3/12 = £9,000 for those three months. Employers may instead use working days or calendar days for part-month pay, so check your contract.

Pro rata holiday entitlement

Almost all workers are entitled to 5.6 weeks of paid holiday a year. Multiply 5.6 by the days you work each week: 5 days gives 28 days, 3 days gives 16.8 days and 2 days gives 11.2 days. Bank holidays can count towards this. Part-time workers must not be treated less favourably than comparable full-time staff, so contractual extras (for example 25 days plus bank holidays) should also be pro-rated.

For irregular-hours and part-year workers, holiday for leave years starting on or after 1 April 2024 can be accrued at 12.07% of hours worked each pay period.

Tax on a pro rata salary

Tax is charged on what you actually earn, not on the full-time equivalent. A part-time salary often falls largely within the £12,570 personal allowance, so the share of pay lost to tax is lower.

Example: £19,200 (60% of £32,000) in England in 2026/27. Income tax is (£19,200 minus £12,570) x 20% = £1,326, NI is £530.40, take-home is £17,343.60, or £1,445.30 a month. That is 90% of gross, compared with about 83% at the full-time £32,000.

Student loan and pension auto-enrolment thresholds are not pro-rated either. Auto-enrolment applies once you earn over £10,000 a year (£833 a month) from one employer.

Common pitfalls

• Comparing a "pro rata" advert with a full-time salary elsewhere: always convert both to an hourly rate.
• Term-time contracts are pro-rated by weeks as well as hours, so annual pay is lower than hours alone suggest.
• Pro rata pay must still meet the minimum wage for every hour worked (£12.71 an hour at 21 and over from April 2026).

Pro rata pay when starting or leaving mid-month

Employers usually use one of three methods for a part month, and your contract or staff handbook should say which.

Example: £30,000 a year (£2,500 a month), starting on 16 June. Calendar days: 15 of 30 days, so £1,250. Working days: if June has 22 working days and you work 11, also £1,250, but the answer differs when weekends fall unevenly. Annual-day rate: £30,000 ÷ 260 working days = £115.38 a day, x 11 = £1,269.23.

When you leave, the same method applies, and you are also paid for any accrued but untaken holiday, worked out pro rata to the part of the holiday year you have worked.

Term-time contracts: pro rata by weeks as well as hours

Term-time pay is usually worked out as full-time salary × (weeks worked + paid holiday weeks) ÷ 52, then × your hours ÷ full-time hours, and paid in 12 equal instalments.

Example: a full-time equivalent of £27,000, 39 term weeks plus 5.6 weeks of statutory holiday, full-time hours. Annual pay is £27,000 × 44.6 ÷ 52 = £23,157.69, or £1,929.81 a month. Working 25 of 37 hours on the same contract reduces it to £15,647.09.

Schools and councils publish their own formula, often in weeks plus a holiday entitlement that rises with service. Ask for the calculation in writing so you can check each part.

Comparing a pro rata job with a full-time one

Compare hourly rates, not annual figures. A £30,000 full-time role at 37.5 hours is £15.38 an hour. A £16,500 role for 20 hours a week is £15.87 an hour, so the part-time job actually pays more per hour.

Then compare what you keep. Because the personal allowance is not pro-rated, the part-time worker keeps a bigger share of each pound.

Your rights as a pro rata worker

The Part-time Workers Regulations 2000 entitle part-time staff to the same hourly pay, holiday, sick pay, pension and training as comparable full-time staff, pro-rated where that makes sense. An employer cannot pay a lower hourly rate just because you work fewer hours.

Overtime is a common grey area. Part-timers are usually paid their normal rate until they pass full-time hours, and only then any overtime premium. That is lawful if full-time colleagues are treated the same way.

Bank holidays when you work set days

Bank holidays are not an extra legal entitlement. GOV.UK says employers can choose to include them in statutory leave, and that they do not have to be given as paid leave at all, so the contract decides.

This matters most for part-timers who do not work Mondays, because four of the eight bank holidays in England and Wales (Easter Monday, the early May, spring and summer bank holidays) always fall on a Monday. Where full-time staff get bank holidays on top of their annual leave, the usual way to avoid treating part-timers less favourably is to add bank holidays to the total pro rata, then have part-timers book the ones that fall on their working days from that total. Ask HR which method applies before booking leave.