How to use the pro rata salary calculator
- Enter the full-time salary for the job, the yearly figure shown in the advert or your contract.
- Choose whether to pro rata by hours or by days, then enter the full-time hours and days and your own. Your days a week are also used for your holiday.
- Enter the full-time holiday in days, including bank holidays, if your employer gives more than the legal minimum.
- If you start or leave during the tax year, add a start date and an end date. The calculator counts the days you are employed between 6 April and 5 April.
- Open Tax year, region, pension and student loans if you live in Scotland, pay into a pension or repay a student loan.
- Read your pro rata take-home pay at the top and switch between year, month and week.
How pro rata pay is worked out
Pro rata means "in proportion". A part-time salary is the full-time salary multiplied by your hours divided by the full-time hours (or your days divided by the full-time days). Part-time workers have the legal right not to be treated less favourably than comparable full-time colleagues, so the hourly rate should be the same.
Part of a year. If you are employed for only part of the tax year, the calculator multiplies the pro rata salary by the days you are employed and divides by the days in the tax year (365 for 2026/27, which runs from 6 April 2026 to 5 April 2027). Many employers work out a part month by working days or calendar days in that month instead, so your first and last payslips may differ slightly.
Holiday. Almost all workers are entitled to 5.6 weeks of paid holiday a year, capped at 28 days. Someone working 3 days a week gets 5.6 × 3 = 16.8 days; someone working 6 days a week still gets 28. Bank holidays can be included in this. If your employer gives full-time staff more, you get the same share: full-time holiday × your proportion of full-time. When you start or leave part way through the holiday year, you get a proportion of the yearly entitlement for the time you work.
Tax. The take-home figures use the 2026/27 rules: a £12,570 Personal Allowance, income tax at 20%, 40% and 45% (or the Scottish rates from 19% to 48%), and National Insurance at 8% between £12,570 and £50,270 a year and 2% above. For part of a year the calculator assumes you had no other taxable income in the tax year, so you get the full allowance through PAYE, while National Insurance and student loan repayments are worked out on each payslip at your normal monthly pay.
Worked example: 3 days a week on a £30,000 salary
A full-time job pays £30,000 for 37.5 hours over 5 days. You work 22.5 hours over 3 days, which is 22.5 ÷ 37.5 = 60%. Your pro rata salary is £30,000 × 60% = £18,000 a year, or £1,500 a month. Income tax is 20% of £5,430 (£18,000 − £12,570) = £1,086, and National Insurance is 8% of £5,430 = £434.40, so take-home pay is £16,479.60 a year (£1,373.30 a month). Your statutory holiday is 5.6 × 3 = 16.8 days, the same as 60% of 28 days.
If you start on 1 September 2026 and stay until the end of the tax year, you are employed for 217 of the 365 days, so you earn £18,000 × 217 ÷ 365 = £10,701.37 in 2026/27. If this is your first job since 6 April, that is below the Personal Allowance, so no income tax is due. National Insurance is different: it is worked out on each payslip, and £1,500 a month is above the monthly threshold of £1,048, so you still pay about £36 a month, £258.26 for the period. Your take-home for the tax year is about £10,443.
Why your payslip might be different
- Part months. Your employer may pay a part month by working days or by calendar days in that month rather than across the whole year.
- National Insurance is per pay period. It is not spread across the tax year like income tax, so in a part year you can pay NI in months you work even if your yearly pay is low.
- Emergency tax code. A new job without a P45 can mean a temporary emergency code until HMRC updates it.
- Holiday pay. Workers with irregular hours or who work only part of the year may have holiday pay added to each payslip instead.
Paid by the hour? Use the UK hourly wage calculator. For every payslip option, including your tax code, a bonus and benefits, use the UK salary calculator. Comparing a full-time and a part-time offer? Try the salary comparison calculator, or work backwards from the take-home you need with the net to gross calculator. More tools are in salary and money calculators.
Frequently asked questions
How do I calculate a pro rata salary?
Divide your weekly hours by the full-time hours and multiply the result by the full-time salary. For example, 22.5 ÷ 37.5 × £30,000 = £18,000 a year.
What does "£30,000 pro rata" mean in a job advert?
It means £30,000 is the full-time salary and you will be paid a share of it based on the hours or days you work. At 3 days out of 5 you would earn £18,000 a year.
How much holiday do part-time workers get?
The legal minimum is 5.6 times the days you work a week, up to 28 days. At 3 days a week that is 16.8 days, at 4 days it is 22.4 days. Bank holidays can count towards it.
Do part-time workers get the full Personal Allowance?
Yes. Everyone gets the same £12,570 tax-free Personal Allowance for the year, so part-time workers often pay a smaller share of their pay in tax than full-time colleagues.
How is pay worked out if I start part way through the year?
You are paid only for the time you are employed. This calculator uses the days employed in the tax year as a share of the whole year; your employer may use working days in the month instead. If it is your first job since 6 April, PAYE normally lets you use the allowance for the months before you started, so your income tax for the year is often low. National Insurance is still worked out on each payslip.
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