Pro-rata salary
Dropping (or adding) hours? See the pro-rata salary and how your take-home changes against the full-time figure.
The change
Full-time vs pro-rata
The pro-rata sum, and what tax does to it
Pro-rata pay is an honest ratio: your new hours divided by full-time hours, applied to the full-time salary. Drop from 37.5 hours to 22.5, three days instead of five, and £40,000 becomes £24,000. HR stops there. Your bank balance shouldn't, because the tax system treats the two salaries differently, and for once the difference is in your favour.
Dropping to three days on £40,000
The personal allowance ignores your hours. Work five days or two, the first £12,570 stays tax free, so on a part-time salary the untaxed slice covers a much bigger share of your pay. Here that means gross pay falls 40% but take-home falls just under 36%: £32,320 a year becomes £20,800. Sixty percent of the hours, 64% of the money you actually see. On a day-rate view you're better paid per day worked than your full-time self, once the taxman has done his bit.
Going the other way
The same arithmetic runs in reverse when you add hours, and this is where people feel cheated. Extra days are taxed at your marginal rate, the top of your pile, while your existing pay enjoys the allowance and the lower bands on average. Going from three days to five never raises take-home by the full two days' pay. If childcare sits on the other side of that ledger, the is it worth working calculator puts the whole equation together. Paid hourly rather than salaried? The hourly wage calculator is built for it, and the take-home pay calculator gives any salary the full treatment, pension and all.
Common questions
How is pro-rata pay calculated?
Take the full-time salary, divide it by the full-time hours, then multiply by the hours you actually work. For example, £30,000 for a 37.5-hour week becomes £24,000 if you work 30 hours. The calculator then shows the take-home on that reduced salary.
Is part-time pay taxed differently?
No. You are taxed on what you actually earn, with the same £12,570 Personal Allowance, so part-time workers often pay a lower effective rate simply because their total income is lower.
Does pro-rata apply to holiday too?
Yes, paid holiday is normally pro-rated to your hours. The full-time statutory minimum of 28 days becomes proportionally fewer days for part-time staff.
These results are estimates for general information only and are not financial advice. Check every figure yourself and seek appropriate advice from a qualified professional before making any decision. Read the full disclaimer.