A pro rata salary is the full-time salary multiplied by the share of full-time hours you will work: and the number on the payslip is that result taxed, not the advert's figure. £30,000 full-time equivalent at three days out of five is £18,000 gross, which keeps £16,479.60 in 2026/27, or £1,373.30 a month. This page works the method; the calculator linked at the end taxes any figure you land on.
The method, in two steps
First, the fraction: your contracted hours divided by the full-time hours for that job. 22.5 over 37.5 is 0.6, three days over five is 0.6, mornings only is usually 0.5. Second, multiply the advertised full-time salary by that fraction. There is no separate tax rate for part-time work; the pro-rated gross goes through exactly the same bands as anyone else's salary, and because the personal allowance does not shrink with your hours, a pro-rated salary usually keeps a larger share of itself than the full-time one.
Worked from £30,000 full-time equivalent
Four days a week (0.8) makes £24,000 gross, keeping £20,799.60: an effective deduction rate of 13.34%. Three days (0.6) makes £18,000, keeping £16,479.60 at 8.45%. Two and a half days (0.5) makes £15,000, keeping £14,319.60 at just 4.54%, because most of it sits inside the £12,570 personal allowance. Note how the share kept RISES as hours fall: that is the allowance doing proportionally more work.
What pro rata does to holiday and the salary band
The same fraction applies to paid holiday: a 0.6 contract accrues 0.6 of the full-time entitlement, and GOV.UK's part-time worker rules require every term of the job: pay, holiday, pension access: to be no less favourable in proportion. When a job advert says "£30,000 pro rata", the £30,000 is the full-time equivalent used for that proportion; your offer letter should state both the FTE figure and your actual gross, and it is the actual gross the tax bands see.
Questions people ask about pro rata salary calculator
Is pro rata pay taxed at a lower rate?
No and yes: the bands are identical, but a smaller gross sits lower in them, so the average rate falls. The £15,000 half-time example above loses only 4.54% where the full-time £30,000 loses 16.27%.
How do I pro-rate a salary for a part year, not part-time hours?
Same idea, different fraction: months worked over twelve, or days over 260. Starting a £30,000 job five months before the year end earns 5/12ths, £12,500, and PAYE spreads your allowance over those months automatically.
Which number do I put into the take-home calculator?
Your actual pro-rated gross (the result of the multiplication), never the full-time equivalent from the advert.