Pro rata salary calculator
Work out what a full-time salary comes to for part-time hours, and what a part-time salary would be worth full time.
Your details
Enter the full-time salary and the two sets of hours.
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Figures checked
How the calculation works
Pro rata means "in proportion". A part-time salary is the full-time salary multiplied by the fraction of full-time hours actually worked. That fraction is the full-time equivalent, usually shortened to FTE.
The arithmetic is: part-time hours divided by full-time hours, multiplied by the full-time salary. Working thirty hours where full-time is thirty-seven and a half gives an FTE of 0.8, so the pro rata salary is eighty per cent of the full-time figure.
The same calculation runs in reverse. If you know what you are paid for part-time hours and want to know what the job is worth full-time, divide rather than multiply. That is the figure to quote when comparing job advertisements, because advertisements almost always give the full-time salary.
Worked examples
| Full-time salary | Full-time hours | Hours worked | FTE | Pro rata salary |
|---|---|---|---|---|
| £35,000.00 | 37.5 | 30 | 0.80 | £28,000.00 |
| £35,000.00 | 37.5 | 22.5 | 0.60 | £21,000.00 |
| £42,000.00 | 40 | 16 | 0.40 | £16,800.00 |
| £28,600.00 | 35 | 28 | 0.80 | £22,880.00 |
The monthly figure is the annual pro rata salary divided by twelve, not by the number of weeks worked. Someone on £28,000.00 pro rata is paid £2,333.33 a month before deductions whether or not their hours are spread evenly.
Days rather than hours
Where a job is advertised in days, use days on both sides of the calculation. Three days out of five is an FTE of 0.6. Mixing the two, for instance dividing days worked by full-time hours, is the commonest mistake and produces a figure that is wildly wrong.
Important rules and exceptions
Holiday is pro rata too, but it is a separate calculation. Statutory holiday is 5.6 weeks of whatever your own week is, so someone working three days a week is entitled to 16.8 days rather than to a fraction of twenty-eight. The holiday entitlement calculator works that out.
Tax and National Insurance are not pro rata. They are worked out on what you actually earn, and because the Personal Allowance is a flat amount rather than a proportion, a part-time worker keeps a larger share of their pay. Use the take-home pay calculator for the figure that reaches your bank account.
Pension contributions, overtime rates and benefits vary. Some benefits are pro rated, some are not, and some have thresholds that a part-time salary does not reach. These are contractual questions rather than statutory ones.
Less favourable treatment is unlawful. The Part-time Workers Regulations mean a part-time worker must not be treated less favourably than a comparable full-time worker without objective justification, in pay rates as in everything else.
Sources, and when we checked them
This calculator uses no statutory figures, only arithmetic, so it does not go out of date in April. The related tax and holiday calculators do, and every figure they use is listed with its date and source on the rates page. Part-time workers' rights: GOV.UK, part-time workers' rights. Checked on 18th September 2026.