When a job is advertised with a full-time salary but the role is part-time, the amount actually paid is often described as a pro rata salary. The idea is simple: you receive the proportion of the full-time salary that corresponds to the proportion of the full-time working pattern you work.
The basic pro rata salary formula
For weekly hours, use:
Pro rata salary = full-time annual salary × (your weekly hours ÷ full-time weekly hours).
For example, if the full-time salary is £30,000 for 37.5 hours per week and you work 22.5 hours:
£30,000 × (22.5 ÷ 37.5) = £18,000.
In this example, 22.5 hours is 60% of 37.5 hours, so the pro rata salary is 60% of £30,000.
Calculating by days per week
If each working day is the same length, you can calculate using days instead. A three-day week compared with a five-day full-time week is 3 ÷ 5 = 0.60 FTE. A £40,000 full-time salary would therefore become £24,000 on a simple three-days-out-of-five basis.
Calculating with FTE
FTE means full-time equivalent. If your contract states 0.8 FTE, a simple salary calculation is full-time salary × 0.8. A £35,000 full-time salary at 0.8 FTE gives £28,000.
Why your payroll figure may differ
A basic pro rata calculation assumes the only difference is the proportion of working time. Real contracts may also take account of term-time working, unpaid weeks, allowances, overtime, salary sacrifice or other arrangements. Always compare a calculator result with the wording of the job offer or contract.
Annual, monthly and weekly figures
Once you know the pro rata annual salary, a simple monthly gross estimate is annual salary ÷ 12 and a simple weekly gross estimate is annual salary ÷ 52. These are planning figures; payroll dates and pay periods can produce slightly different amounts in individual payslips.
Use the calculator
For an instant result, use the Pro Rata Calculator UK on our homepage. It shows the proportion, FTE and the formula used so you can check the calculation yourself.
Important: This article is general information, not personalised financial, tax, payroll, employment or legal advice. Check important figures against your contract and current official guidance.