Pro-rata salary calculator UK

A pro-rata salary is a salary proportionally adjusted to reflect fewer hours or fewer weeks than the standard full-time arrangement. It is calculated by multiplying the full-time salary by the fraction of full-time hours worked. For example, working 25 hours out of a full-time 37.5 gives a pro-rata salary of 66.7% of the full-time amount.

Divide your actual hours per week by the full-time hours per week, then multiply by the full-time annual salary. Example: (25 hours / 37.5 hours) x £35,000 = £23,333 pro-rata. For a new starter part-way through the year, divide the annual salary by 52 and multiply by the weeks remaining: (£35,000 / 52) x 26 = £17,500.

Income Tax and National Insurance are calculated on your actual pro-rata earnings, not the full-time equivalent. The personal allowance (£12,570 in 2025/26) applies in full, so part-time workers earning less than this threshold pay no Income Tax. If you earn between £12,570 and £50,270, you pay 20% Income Tax on the amount above the personal allowance, plus 8% National Insurance on earnings above £12,570.

Yes. The personal allowance (£12,570 for 2025/26) is not reduced for part-time workers. A part-time employee earning £15,000 a year pays Income Tax on the same £2,430 above the personal allowance as a full-time employee earning the same amount. This means part-time workers often pay a lower effective tax rate than their full-time-equivalent salary would suggest.

On a pro-rata salary of £20,000 in 2025/26 with a standard 1257L tax code, take-home pay after Income Tax and National Insurance is approximately £17,100 per year, or around £1,425 per month. Enter your exact figures into the calculator above to see a precise breakdown.