Pro Rata Salary Calculator
Use this UK pro rata salary calculator to scale a full-time annual salary down by your part-time weekly hours. Pro rata salary = full-time salary × part-time hours ÷ full-time hours. For example £30,000 × 22.5 ÷ 37.5 = £18,000 pro rata. Shows annual, monthly and weekly gross pay. Estimates only.
A focused UK pro rata salary calculator for part-time and reduced-hours roles. Enter your full-time salary and weekly hours, plus your part-time weekly hours, and see the proportional annual, monthly and weekly gross figures.
Note: Gross figures only — Income Tax, National Insurance and pension contributions are not deducted.
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What this calculator does
Returns the pro rata annual salary, monthly gross, weekly gross, percentage of full-time hours and difference vs the full-time figure, calculated from full-time salary, full-time hours and part-time hours.
Who it is for
UK employees switching from full-time to part-time, candidates evaluating part-time job offers, HR teams pricing reduced-hours offers, and parents returning to work after maternity, paternity or shared parental leave.
How to use it
Enter the full-time annual salary, the full-time weekly hours for the role and your part-time weekly hours. Results update instantly. Use the reset button to restore defaults (£30,000, 37.5 hrs, 22.5 hrs) or the copy button to share results.
How the calculation works
Pro rata annual salary = full-time salary × part-time hours ÷ full-time hours. Monthly gross = pro rata annual ÷ 12. Weekly gross = pro rata annual ÷ 52. Percentage of full-time = part-time hours ÷ full-time hours × 100. Difference = full-time salary − pro rata annual.
Worked example
Full-time £30,000, full-time 37.5 hrs/week, part-time 22.5 hrs/week. Pro rata annual = £30,000 × 22.5 ÷ 37.5 = £18,000. Monthly = £1,500. Weekly ≈ £346.15. Percentage of full-time = 60.0%. Difference vs full-time = £12,000.
Assumptions and limitations
- Gross pay only — before Income Tax, NI and pension
- Assumes the same weekly hours every working week of the year
- Monthly uses annual ÷ 12, weekly uses annual ÷ 52
- Does not include bonuses, overtime, salary sacrifice or allowances
- For irregular-hours or part-year work, use the 12.07% accrual method (separate from this calculator)
Frequently asked questions
How is pro rata salary calculated in the UK?
Divide your part-time hours by the full-time hours, then multiply by the full-time annual salary. £30,000 × 22.5 ÷ 37.5 = £18,000 pro rata.
Is pro rata salary gross or net?
Gross — before Income Tax, National Insurance and pension contributions.
Does the calculator work for compressed hours?
If your weekly hours match the full-time equivalent, you are at 100% — your salary should not be reduced. The calculator handles this automatically.
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Sources and references
GOV.UK: PAYE and pay-period guidance for converting annual gross pay to monthly and weekly equivalents. ACAS: Pro rata pay and reduced-hours working guidance. General reference only — not legal or tax advice.
Last updated
Last reviewed: 2026-05-20.