Career & HR
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Pro-Rata Salary Calculator
Work out fair pay for part-time or mid-month joins. Accurate, instant and free — for United Kingdom.
What these mean:
Working 22.5 of 37.5 hours/week — 60% FTE — gives you £21,000 gross per year.
How pro-rata salary is calculated
A pro-rata salary applies a proportion (FTE fraction) to the full-time equivalent annual salary. There are three recognised methods — all are lawful as long as the employer uses one method consistently across comparable staff.
Hours per week
The most precise method
The hourly rate must always match a full-timer’s — that’s a statutory requirement under the Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000.
Days per week
When daily hours are equal
e.g. 3 5 0.60
Gives the same result as the hours method when daily hours are consistent across the week. Where shift patterns vary, the hours method is more accurate.
Partial year
New starters and leavers
Working-days basis (default, fairer)
Calendar-days basis (if your contract specifies it)
Working days (260 Mon–Fri days) is the recommended default. Using 365 calendar days puts weekends in the denominator, which can understate the daily rate for days you actually work. Croner and DavidsonMorris both confirm that the working-days basis is the standard default, and that employers must apply their chosen method consistently.
Pro-rata statutory holiday (UK)
5.6 weeks, capped at 28 days
Under GOV.UK guidance, UK statutory minimum holiday is 5.6 weeks per year, capped at 28 days for a standard 5-day week. Part-time workers get a proportionate share:
e.g. 3 days/week → 16.8 days
Equivalently: 5.6 weeks × days per week (e.g. 5.6 × 3 = 16.8). Holiday is shown to one decimal place and is capped so it never exceeds the full-time entitlement.
A full pro-rata calculation, step by step
A role is advertised at £35,000 FTE. Full-time hours are 37.5 hrs/week (5 days). The employee works 22.5 hrs/week over 3 days.
- 1Proportion: 22.5 ÷ 37.5 = 0.60 (60% FTE). Days check: 3 ÷ 5 = 0.60 — matches.
- 2Pro-rata annual salary: £35,000 × 0.60 = £21,000.
- 3Equivalent hourly rate: £35,000 ÷ (37.5 × 52) = £35,000 ÷ 1,950 = £17.95/hour — the same as a full-timer, as required by law. Cross-check: £17.95 × 22.5 × 52 ≈ £21,000. ✓
- 4Monthly gross pay: £21,000 ÷ 12 = £1,750/month (before Income Tax and National Insurance).
- 5Pro-rata holiday: 28 × 0.60 = 16.8 days. Equivalently: 5.6 weeks × 3 days = 16.8 days. ✓
Partial-year add-on: Same person starts 1 October 2026. Working-days basis, ~260 working days in the year, ~65 working days from 1 Oct to 31 Dec. Pay for the period = (£21,000 ÷ 260) × 65 = £5,250 (roughly one quarter of the annual salary — consistent, since Oct–Dec is about ¼ of the working year).
These are gross figures
Frequently asked questions
Pro rata means "in proportion". When a job advert lists a salary as "pro rata", it means the figure shown is the full-time equivalent (FTE) annual salary and your actual pay will be a proportionate share of it based on your hours or days worked. For example, a role advertised at £35,000 pro rata (FTE, 37.5 hrs/week) pays £21,000 for someone working 22.5 hrs/week (60% of full-time).
UK statutory holiday is 5.6 weeks per year, capped at 28 days for a 5-day week. Part-time workers receive the same proportion of holiday as their hours or days bear to full-time. The formula is: pro-rata holiday = full-time holiday days × (part-time days per week ÷ full-time days per week). For 3 days a week: 28 × (3 ÷ 5) = 16.8 days. This is a statutory right under GOV.UK guidance and the Part-time Workers Regulations 2000.
Working days (typically 260 Mon–Fri days per year) is the fairer and more widely used default, because it reflects the days you are actually contracted to work. Calendar days (365) can slightly understate your pay because weekends are included in the denominator. Employers must apply one method consistently across all staff. If your contract specifies calendar days, use the calendar-days setting in this calculator.
This calculator shows gross salary — the figure before Income Tax and National Insurance come out. Your actual take-home pay depends on your tax code, student loan status, pension contributions, and other deductions. Use the Take-Home Salary Calculator to see what actually lands in your bank.
Yes. Under the Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000, part-time employees must receive the same hourly rate as comparable full-time colleagues. The pro-rata principle scales pay proportionally, which preserves the hourly rate. For example, a £35,000 FTE role at 37.5 hrs/week gives an hourly rate of £17.95/hour regardless of whether you work 37.5 hrs or 22.5 hrs per week.
Method, assumptions & references
Methodology note: formulas follow standard UK HR/payroll practice (Croner; DavidsonMorris) and statutory anchors from GOV.UK and the Part-time Workers Regulations 2000. All salary figures are gross estimates — not legal or tax advice. Employers should confirm the contractual calculation method with their payroll provider.
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