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Tax & Salary · UK 37.5h default

Pro Rata Salary Calculator

A job is advertised at a full-time rate but you’re working fewer hours. This tells you the actual gross salary in your contract — and what it works out to per month, week and day.

Your hours

£
hrs
hrs

The UK norm is 37.5 hours (excluding lunch). Some roles use 35 or 40.

Your pro-rata salary

£32,000(80.0%)

Pro-rata breakdown

  • Per year (gross)
    £32,000
  • Per month
    £2,667
  • Per week
    £615
  • Per working day
    Assumes a 5-day week.
    £123

This is your gross (pre-tax) figure. Run it through the salary calculator to see take-home pay.

How we calculated your result

Pro-rata means “in proportion.” The calculation is simple:

Pro-rata salary = Full-time salary × (Your hours ÷ Full-time hours)

We then divide the annual figure by 12 for monthly, 52 for weekly, and 260 (52 × 5) for a daily working-day rate.

For example: a £40,000 full-time role at 37.5 hours/week, done at 30 hours/week, is 30 ÷ 37.5 = 0.8 = 80%, giving £32,000.

Official UK rules in simple English

There’s no single statutory definition of full-time in the UK, but the common-law and ACAS expectation is:

  • Full-time is usually 35–40 hours/week. Civil service and many offices use 37 or 37.5; healthcare often uses 37.5; finance and law commonly use 40.
  • Part-time workers have the legal right not to be treated less favourably than comparable full-timers on a pro-rata basis (Part-time Workers Regulations 2000).
  • Holiday entitlement is also pro-rated. The statutory minimum is 5.6 weeks (28 days for a 5-day full-time week), reduced proportionally for fewer days.

Common pitfalls to watch out for

  • ⚠ Lunch breaks aren't usually paid

    A “9-to-5” job with a 1-hour unpaid lunch is 35 paid hours/week, not 40. Check whether the advertised hours include or exclude breaks before you calculate.

  • ⚠ Compressed hours ≠ part time

    Working a full-time job’s hours over four longer days (e.g. 4×9.25h = 37 hours) is still full time — you’re entitled to the full salary, not 80% of it.

  • ⚠ Tax thresholds don't pro-rate

    Your Personal Allowance (£12,570) and NI thresholds are annual figures. If your pro-rata salary lands you below them, you pay no tax at all on that income.

  • ⚠ Holiday and bank holidays should also be pro-rated

    Don’t accept the same paid leave as full-time colleagues by default — but equally, employers shouldn’t under-count it. The fair calculation is 5.6 weeks × the fraction of full-time hours you work.

Frequently asked questions

Is pro-rata always based on hours, or can it be days?
Either is valid. Many employers calculate pro-rata by days (e.g. 4 days out of 5 = 80%), which usually matches hours-based when daily hours are equal. Always confirm in the offer letter.
Does my pension contribution rate change?
No — auto-enrolment uses the percentage of your actual qualifying earnings, which are already lower because you earn less. The 8% combined minimum applies the same way.
What about overtime above my contracted hours?
Overtime is paid on top of your pro-rata salary, usually at your normal hourly rate up to full-time hours and at an enhanced rate (1.25× or 1.5×) beyond that. Check your contract for the specifics.

Gross figures only. Use the salary calculator for take-home pay after Income Tax, NI and pension.

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