Pro Rata Salary Calculator
A job advertised at a full-time salary pays proportionally less if you work fewer hours. Enter the full-time salary and hours, then your actual hours, to see your pro-rata gross pay — and what it means after tax. Because tax bands do not shrink with your hours, the after-tax picture is usually better than the simple fraction suggests.
How it works
Pro-rata pay = full-time salary × (your hours ÷ full-time hours). A £30,000 FTE role at 37.5 hours worked 20 hours a week pays £16,000 gross. Holiday entitlement scales the same way.
A fully worked example: suppose the advert says £30,000 FTE on a 37.5-hour week and you will work three days (22.5 hours). The fraction is 22.5 ÷ 37.5 = 0.6, so your gross pay is £18,000. Your income tax at 2026/27 rates is 20% of the £5,430 above the £12,570 Personal Allowance — £1,086 — and National Insurance is 8% of the same £5,430, which is £434.40, leaving take-home of £16,479.60.
The tax outcome is disproportionately favourable for part-timers: the £12,570 Personal Allowance does not shrink, so a larger share of a part-time salary is tax-free. £16,000 part-time keeps about 94% of gross, while the full £30,000 keeps about 85%.
An edge case worth knowing: if your pro-rata gross falls below £12,570, you pay no income tax at all — and because the employee National Insurance threshold is also £12,570, no NI either. On the £30,000 FTE example, anyone working 15 hours or fewer of the 37.5 (£12,000 gross or less) takes home every pound they earn.
This calculator assumes hours-based pro-rating, the standard approach. Some employers pro-rate by days worked — the arithmetic is the same with days in place of hours. A three-day week against a five-day full-time role is simply a fraction of 3 ÷ 5 = 0.6.
Two common mistakes: reading the advertised FTE figure as your actual pay (the advert's salary is what a full-timer gets), and assuming the advert's full-time baseline. A 30-hour week is 80% of a 37.5-hour baseline but only 75% of a 40-hour one — on £30,000 FTE that is the difference between £24,000 and £22,500, so always check which baseline the employer uses.
The result is your pro-rata gross salary, with the take-home estimate applying 2026/27 income tax and employee National Insurance only — the two deductions covered by the official rates cited below. Pension contributions and student loan repayments are separate deductions on top.
FAQ
How do I work out pro rata salary?
Divide your weekly hours by the full-time hours and multiply by the advertised salary. Example: 25 hours on a 37.5-hour, £33,000 FTE role = 25 ÷ 37.5 × £33,000 = £22,000 gross. Holiday days, pension contributions and bonuses normally scale by the same fraction.
What does "£30,000 pro rata" mean in a job advert?
It means £30,000 is the full-time equivalent (FTE) — you receive the proportion matching your hours. At 22.5 hours against a 37.5-hour full-time week you would actually be paid £18,000 a year. Always check the advert's full-time hours, as 35, 37.5 and 40-hour baselines change the result.
Is tax also pro-rated for part-time workers?
No — tax bands and the Personal Allowance stay the same regardless of hours, which works in your favour: a bigger fraction of a smaller salary sits inside the tax-free £12,570. Working 50% of hours therefore leaves you with more than 50% of the full-time take-home pay.
How is pro rata calculated by days instead of hours?
Exactly the same way, with days as the fraction: days you work ÷ full-time days × FTE salary. A three-day week against a five-day full-time role is 3 ÷ 5 = 0.6, so a £30,000 FTE post pays £18,000. Employers who pro-rate by days and by hours should arrive at the same figure when the daily hours are equal.
Do part-time workers get holiday, pension and bonuses pro rata?
Normally yes — holiday entitlement, employer pension contributions and bonuses scale by the same fraction as your pay. If a full-timer on your grade gets 25 days of holiday, a 60% contract would come with 15 days. Check your contract, as the fraction should be stated alongside the salary.
What if my pro-rata salary is below the Personal Allowance?
Then you pay no income tax at all: everything up to £12,570 a year is tax-free, and the employee National Insurance threshold sits at the same £12,570, so no NI is due either. Gross and take-home are identical at that level — one reason short part-time contracts can be surprisingly tax-efficient.
Why is my take-home more than the same fraction of the full-time take-home?
Because the £12,570 tax-free allowance does not shrink with your hours. On a £30,000 FTE role, someone working half the hours earns £15,000 — 50% of the gross — but a much larger share of that £15,000 sits inside the allowance than for the full-timer, so their take-home is comfortably above 50% of the full-time net figure.