izharshah.com/tools/pro-rata-salary-calculator · The Parallel Operator · Pro rata salary calculator · Tax year 2026/27, checked against GOV.UK 20 September 2026
Pro rata salary: what you actually get paid
Enter the full-time salary and the hours you actually work. You get the pro rata salary, the take-home after income tax and National Insurance, your hourly rate and your holiday entitlement. National Insurance is worked out per payslip, which is what makes a part-year start come out right.
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Unlock the full comparison: your pay set against the full-time figure, what each payslip looks like, your hourly rate against the minimum wage, and your holiday entitlement. Save or print it as a PDF to keep.
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Your full breakdown
Thank you, you are on the list. Here is your full breakdown.
| Full time | Your pay |
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| Every payslip | Amount |
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How this calculator works
The pro rata salary is the full-time salary multiplied by the share of full-time hours you actually work. Twenty-two and a half hours against a 37.5-hour week is 0.6, so a £38,000 job pays £22,800. Days work the same way: three days out of five is also 0.6.
There is no legal definition of a full-time week. Thirty-five, 37.5 and 40 hours are all common, and the choice changes the answer. The same 22.5 hours is 0.6 of a 37.5-hour week but 0.5625 of a 40-hour week, a difference of £1,425 a year on a £38,000 salary. That is why the full-time hours field is on the page rather than hidden behind a default. Use the figure in your contract. GOV.UK only sets an upper limit, an average of 48 hours a week over 17 weeks.
Tax and National Insurance do not scale the same way. Income tax is worked out across the whole year, and your £12,570 personal allowance is not reduced because you work part time or started in October. National Insurance is different: it is charged on what you earn in each pay period and is never added up and reconciled at the end of the year. So this page works National Insurance out one payslip at a time and multiplies, using the £1,048 a month threshold rather than the £12,570 annual one. On a part-year start the difference is large: treating it as an annual sum can understate National Insurance by hundreds of pounds.
Part-year figures use the paydays that actually fall inside this tax year. Pay for the first few days of April normally arrives on the April payday, which sits in the next tax year, so counting calendar days to 5 April overstates what you will be paid. The full breakdown shows the calendar-day figure too, because that is the right basis for pro-rating a bonus or an allowance.
What it does not cover: overtime, shift premiums, bonuses, benefits in kind, salary sacrifice, tax codes other than the standard 1257L, or a part month at the very start or end of a job, where employers variously divide by 260 working days, by 365 calendar days, or by the days in that particular month, and the contract decides. Term-time-only and annualised-hours contracts are not covered either. It is guidance, not employment or tax advice.
Questions people ask about pro rata pay
How do I work out my pro rata salary from a full-time salary?
Divide your hours by the full-time hours, then multiply the full-time salary by that fraction. Twenty-two and a half hours against 37.5 is 0.6, and 0.6 of £38,000 is £22,800. Use days instead of hours only if all your days are the same length.
What is £30,000 pro rata for 3 days a week?
Three days out of five is 0.6, so £18,000 a year. After income tax and National Insurance that is about £16,140 take-home, or roughly £1,345 a month. Type £30,000 and 3 days above to see it with your own pension and student loan.
Does working part time mean I pay less tax and National Insurance?
Less of both, and proportionally less than you might expect, because the first £12,570 is still tax free. Your personal allowance is not reduced for working part time. National Insurance falls too, since it is charged only on what each payslip exceeds £1,048 a month.
How is my first month's pay calculated if I start mid month?
Your employer pro-rates that one payslip, but there is no single legal method. Some divide the annual salary by 260 working days and pay you for the days worked, some use the calendar days in that month, some use 365. They give different answers and your contract decides, so treat a first part month as an estimate.
How much holiday am I entitled to if I work part time?
5.6 weeks of your own working week. Three days a week gives 16.8 days a year, and the 28-day cap only bites at five days a week or more. Bank holidays can be counted inside that 5.6 weeks, so check whether yours are on top or included.
Related tools
Guidance only, not employment or tax advice. Your contract and your employer's payroll decide the final figures, and the conventions used for part months vary between employers.
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