How it works
What does pro rata mean?
Pro rata is Latin for “in proportion”. When a UK job advert says “£30,000 pro rata”, it means £30,000 is the full-time equivalent (FTE) salary — and you will be paid the proportion of it that matches your working pattern. Work 60% of full-time hours, earn 60% of the salary.
The phrase appears in three common situations: part-time roles (fewer days or hours per week than the full-time norm), term-time-only roles (school support staff paid for fewer weeks per year), and partial years (starting or leaving a job mid-way through the year, or an unpaid career break).
Pro rata applies to more than the headline salary. Holiday entitlement, bonuses, benefits and even redundancy pay are typically pro-rated on the same basis — a right protected by the Part-time Workers Regulations 2000, covered below. What is not pro-rated is your tax-free Personal Allowance: a part-timer keeps the full £12,570 (2026/27), which is why part-time work is taxed proportionally more lightly.
Convert the result into a monthly or hourly figure with the salary to hourly calculator, and see what actually lands in your bank with the PAYE take-home calculator.
The pro rata formula, with three worked examples
The formula is a single ratio: pro rata salary = FTE salary × (your hours ÷ full-time hours). You can run it on days per week, hours per week, or weeks per year — whichever unit describes the difference between your pattern and full-time.
| Scenario | Calculation | Pro rata salary | Monthly |
|---|---|---|---|
| 3 days a week on £30,000 FTE (5-day norm) | £30,000 × 3 ÷ 5 | £18,000 | £1,500.00 |
| 22.5 hours a week on £30,000 FTE (37.5-hour norm) | £30,000 × 22.5 ÷ 37.5 | £18,000 | £1,500.00 |
| Term-time only: 39 weeks + 5.6 weeks paid holiday, £22,000 FTE | £22,000 × 44.6 ÷ 52 | £18,869.23 | £1,572.44 |
| Mid-year starter: joins 1 October on £32,000 | £32,000 × 6 ÷ 12 | £16,000 (for that tax year) | £2,666.67 while employed |
Example 1 — part-time days: £30,000 FTE, 3 days a week
You work 3 of the standard 5 days, so the ratio is 3/5 = 0.6. Pro rata salary: £30,000 × 0.6 = £18,000 a year, paid as £1,500 a month. Your hourly rate is unchanged — you earn the same per hour as your full-time colleague, just for fewer hours.
Example 2 — term-time only: £22,000 FTE, 39 working weeks
A teaching assistant works 39 term weeks but is still entitled to 5.6 weeks of paid statutory holiday, so the paid year is 39 + 5.6 = 44.6 weeks. Pro rata salary: £22,000 × 44.6 ÷ 52 = £18,869.23, usually spread evenly across 12 monthly payslips so income is stable through the school holidays.
Example 3 — mid-year starter: £32,000, joining 1 October
You are full-time, but only employed for 6 of the 12 months in the year. You earn the full £2,666.67 a month while employed, and £16,000 across the tax year. Payroll systems often pro-rate the first partial month by calendar days: joining on the 15th of a 30-day month pays 16/30 of that month’s salary.
Pro rata holiday entitlement: 5.6 weeks, scaled to your pattern
Every UK worker gets a statutory minimum of 5.6 weeks’ paid holiday a year, and for part-timers that entitlement is pro-rated using the same logic as salary. The GOV.UK method for fixed days is simply 5.6 × days worked per week: 3 days a week gives 3 × 5.6 = 16.8 days of paid holiday. For fixed hours, use 5.6 × weekly hours instead.
Two details trip people up. First, the statutory entitlement is capped at 28 days, so someone working 6 days a week still gets 28, not 33.6. Second, since April 2024, workers with irregular hours or part-year contracts accrue holiday at 12.07% of hours worked in each pay period instead. GOV.UK publishes an official holiday entitlement calculator that handles starts, leavers and irregular patterns.
A part-time worker cannot be given less favourable holiday terms per hour than a full-timer — see the holiday pay calculator for what each day of leave is actually worth in pay.
| Days worked per week | Statutory holiday (days) | Notes |
|---|---|---|
| 5 | 28 | 5 × 5.6 = 28 — the cap |
| 4 | 22.4 | Usually rounded up to 22.5 or 23 |
| 3 | 16.8 | Round up, never down, to stay compliant |
| 2 | 11.2 | |
| 1 | 5.6 | |
| 6 | 28 | Capped — 6 × 5.6 = 33.6 but the statutory max is 28 |
Pro rata and tax: the Personal Allowance is NOT pro-rated
You are taxed on what you actually earn, not on the FTE figure — and, crucially, the £12,570 Personal Allowance is never pro-rated. A part-timer earning £18,000 uses the same full £12,570 tax-free allowance as a full-timer on £30,000. That makes part-time pay disproportionately tax-efficient.
On the £18,000 pro rata salary from Example 1 (2026/27, England): taxable income is £18,000 − £12,570 = £5,430. Income Tax at 20% is £1,086 and National Insurance at 8% is £434.40, leaving £16,479.60 net — you keep 91.6% of gross, versus about 85% for the £30,000 full-timer. Check your own figures with the income tax calculator and national insurance calculator.
Your tax code (normally 1257L) also does not change because you go part-time. One caveat for mid-year starters: PAYE spreads the allowance across the year, so your first payslips may over- or under-tax you slightly until the cumulative calculation catches up — any difference washes out automatically or is refunded by HMRC.
Sick pay, pensions and benefits: what else gets pro-rated
Statutory Sick Pay (SSP) is a flat weekly rate, not a percentage of salary — you qualify if your average earnings reach the Lower Earnings Limit, and part-timers who qualify get the same weekly SSP as full-timers (it is divided across your qualifying days). Occupational sick pay schemes, by contrast, usually pay “full salary”, meaning your pro rata salary.
Workplace pensions scale naturally: auto-enrolment contributions are a percentage of your actual qualifying earnings, so a part-timer contributes and receives proportionally less in cash but the same in percentage terms. Note the auto-enrolment earnings trigger of £10,000 — a very part-time role may fall below it, though you can usually opt in. Model contributions with the pension contribution calculator.
Contractual benefits — bonuses, car allowances, private medical excess days, redundancy pay — are typically pro-rated by hours. Under the pro rata principle in the Part-time Workers Regulations, that proportional treatment is exactly what the law expects: not identical amounts, but the same rate.
Common pro rata mistakes (and how to avoid them)
Most pro rata disputes come from small arithmetic choices rather than bad faith. Five errors account for nearly all of them.
- Dividing by 12 when the contract works in weeks. £30,000 ÷ 12 = £2,500/month, but £30,000 ÷ 52 = £576.92/week — and 4 weeks of that is £2,307.69, not £2,500. Months are not 4 weeks long (they average 4.33). Use weeks for weekly-paid roles and months for salaried ones, never mix.
- Counting unpaid lunch breaks as working hours. A “9 to 5” day with a 1-hour unpaid lunch is 7 paid hours, not 8. On a 35-hour full-time norm, assuming 40 understates your ratio and your pay.
- Using the wrong full-time norm. Some employers use 35 hours, others 37.5 or 40. £30,000 × 22.5/37.5 = £18,000 but £30,000 × 22.5/40 = £16,875. Always confirm the FTE hours in writing.
- Rounding holiday down. 16.8 days must be rounded up (or converted to hours), never down to 16 — rounding down breaches the statutory minimum.
- Forgetting bank holidays for part-timers. If full-timers get bank holidays off in addition to leave, part-timers must get a pro-rated equivalent even when the bank holiday falls on a day they never work (most fall on Mondays, disadvantaging people who don’t work Mondays).
Your rights: the Part-time Workers Regulations 2000
The Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000 make it unlawful to treat a part-time worker less favourably than a comparable full-time worker doing the same job, unless the employer can objectively justify the difference. Regulation 5 embeds the pro rata principle: a part-timer must receive at least the same proportion of pay and benefits as their hours bear to full-time hours.
That covers hourly pay, overtime rates once full-time hours are exceeded, bonuses, pension access, holiday, training and promotion opportunities. If you believe you are being under-paid pro rata, ask your employer for a written statement of reasons, raise it with ACAS, and note that tribunal claims must normally be brought within three months less one day of the treatment.
Related tools: the hourly wage calculator verifies that your hourly rate matches your full-time colleagues’, and the pro rata salary calculator itself handles any hours/weeks combination.