Pro rata salary calculator

"Pro rata" means the advertised salary is the full-time one. On a 37.5-hour week, working 22.5 hours is 60% of full time — so £35,000 pro rata pays £21,000 a year, or £1,750.00 a month. The hourly rate is £17.95 whichever hours you work.

How this is worked out

Pro rata is one division and one multiplication: your hours divided by the full-time hours gives the fraction, and the full-time salary multiplied by that fraction gives the pay. Everything else on the page follows from it — the monthly figure is a twelfth of the year, the weekly figure is the year divided by the weeks your employer pays, and the hourly rate is the full-time salary reduced to a single hour. The hourly rate is worked out from the full-time salary rather than from the rounded pro rata one, so that the two routes agree to the penny; that identity is the definition of pro rata and the thing worth checking a payslip against.

A role advertised at £35,000 pro rata, full time 37.5 hours, working 22.5 hours a week

1. 22.5 hours divided by 37.5 is 0.6 — you would work 60% of a full week.
2. £35,000 × 0.6 = £21,000 a year, which is the figure that would appear on a contract.
3. A twelfth of that is £1,750 a month before tax.
4. The hourly rate is £35,000 ÷ 52 weeks ÷ 37.5 hours = £17.95, and it is the same whether you work 22.5 hours or 37.5.

Weekly and hourly figures divide by 52 weeks, the usual UK payroll convention. It is a convention rather than a fact — 365 ÷ 7 gives 52.143, which some employers use instead — so the page states which one it used rather than leaving a quiet third of a per cent unexplained.

Why there is nothing to cite here

Pro rata is a ratio, not a rate. There is no threshold to look up and no figure that changes in April, so this page has no source to go stale and needs no annual check. The moment tax enters the picture that stops being true, which is why the take-home pay calculator is a separate page that cites HMRC and carries a date.

What catches people out

• "£35,000 pro rata" in a job advert is the full-time salary, not the salary. It is what someone doing the whole week would earn, and the advert is telling you the part-time pay will be a fraction of it. This is the single most common misunderstanding of the phrase, and it is worth working out the actual figure before an interview rather than after an offer.
• A four-day week is not automatically 80% of the pay. It is 80% if the hours drop from five days to four, and it is 100% if the same hours are compressed into four longer days. Those are completely different arrangements that get described with the same words, which is why this asks for hours rather than days.
• Term-time-only pay is not a simple hours calculation. Staff working school terms are pro rata on weeks as well as hours, and the weeks figure has to include paid holiday entitlement — which is why a term-time salary is usually a larger fraction of full-time than the raw ratio of weeks suggests. If your contract states a percentage, use that rather than deriving one here.
• Part-time staff are entitled to bank holidays pro rata. Someone who never works Mondays would otherwise lose most of them, so the entitlement is normally converted into hours and added to leave. It does not change salary, but it is the part people are most often quietly short-changed on.
• Weeks in a year is a convention, not a fact. Dividing a salary into weekly pay uses 52 in most UK payrolls, but 52.143 is 365÷7 and some employers use it. On £40,000 the two disagree by about £130 a year, so this page states which one it used rather than leaving you to wonder.

Questions

What does "pro rata" actually mean on a job advert?

It means "in proportion". The salary quoted is the full-time equivalent — what the role pays for a whole working week — and your pay will be that figure scaled to the hours you actually work.

So an advert saying "£35,000 pro rata, 22.5 hours" is offering £21,000 if full time is 37.5 hours. The larger number is the one that gets remembered, which is exactly why it is worth doing the arithmetic.

How do I check my hourly rate is right?

Divide the full-time salary by the number of weeks your employer pays in a year, then by the full-time weekly hours. Working part time must not change that figure — an identical hourly rate is the whole definition of pro rata.

If your hourly rate comes out lower than a full-time colleague doing the same job, that is not a rounding difference. Part-time workers have a statutory right not to be treated less favourably on pay.

Is a four-day week 80% of the salary?

Only if you are working 80% of the hours. Dropping from 37.5 hours over five days to 30 hours over four is 80%, and the pay follows. Compressing the same 37.5 hours into four longer days is not a reduction in hours at all, and the pay should not change.

Some employers also run a four-day week at full pay as a productivity arrangement. That is a contractual choice rather than arithmetic, and no calculator can tell you which one you have been offered.

Does my take-home pay scale the same way?

No, and this is where pro rata stops being a simple ratio. Income tax and National Insurance both have thresholds that do not scale, so halving your salary usually more than halves the tax — the personal allowance covers a much larger share of a smaller salary.

Work out the pro rata figure here, then put it through the take-home pay calculator to see what actually arrives.

Why does this ask for hours rather than days?

Because days are ambiguous and hours are not. "Three days a week" could be 22.5 hours or 24 or 30 depending on the length of a day, and a compressed week has fewer days at the same total hours.

Hours give one answer. If you only know your days, multiply by the length of your working day first.

What you would actually take home

Work out the next thing

• Statutory redundancy payWorked out year by year, because the rate depends on the age you were during each year of service rather than your age when the job ends.
• Take-home payGross salary in, every deduction itemised out — income tax band by band, National Insurance, student loan, pension.
• Pay riseWhat a rise or a bonus is actually worth in your bank account, and the marginal rate that decides it.