Reviewed for UK readers: September 2026.
Pro rata hours show what proportion of a full-time working pattern someone works. If a full-time role is 37.5 hours a week and you work 30 hours, your working fraction is 0.8 FTE, or 80%. You can enter those figures in our pro rata calculator UK to see the corresponding salary instantly.
The same ratio is useful for comparing vacancies, checking part-time salary offers and understanding benefits that are explicitly applied in proportion to hours.
Quick answer
- Hours ratio = your weekly hours ÷ full-time weekly hours.
- Multiply the ratio by 100 to get your work percentage.
- Multiply an FTE salary by the ratio to estimate pro rata salary.
- Do not assume every benefit is reduced by the same ratio; check the contract.
Pro rata hours formula
Use Your contracted weekly hours ÷ Full-time weekly hours. For 30 hours in a 37.5-hour organisation, 30 ÷ 37.5 = 0.8. That is 0.8 FTE or 80% of full time.
Examples for common UK working weeks
If full time is 35 hours, 21 hours is 60% FTE, 28 hours is 80% and 31.5 hours is 90%. If full time is 37.5 hours, 22.5 hours is 60%, 30 hours is 80% and 33.75 hours is 90%. If full time is 40 hours, 24 hours is 60%, 32 hours is 80% and 36 hours is 90%.
Using hours to calculate salary
Once you have the hours ratio, multiply it by the full-time salary. A £40,000 FTE salary at 0.8 FTE gives an estimated gross annual salary of £32,000. Monthly gross pay before deductions is £32,000 ÷ 12 = about £2,666.67.
Hours are not always the whole story
Term-time roles, compressed hours, job shares and irregular-hour contracts can require extra steps. If a job is term-time only, the annual salary may also reflect paid weeks. If someone works the same full-time total hours over fewer days, they may still be 1.0 FTE even though they attend fewer days.
Part-time worker protections
GOV.UK states that part-time workers should not be treated less favourably than comparable full-time workers simply because they are part-time. Some benefits can be applied pro rata, so the relevant comparator and contract wording matter.
Common hours and FTE mistakes
Use paid contracted hours, not the time you are physically at work if unpaid breaks are excluded. Also do not assume that fewer attendance days means lower FTE: compressed-hours staff may work the full weekly hours across fewer days.
When comparing two jobs, convert both to FTE and an annual salary first. Then compare holiday, pension and other benefits separately instead of mixing them into the basic hours calculation.
Use the calculator
For a quick gross salary estimate, use the Pro Rata Calculator UK. Enter the full-time salary and your hours, days or FTE, then compare the result with your contract or payroll figure.
Other working patterns: 20 hours a week · 24 hours a week · 30 hours a week · 37.5-hour week · 40-hour week · 2 days a week · 3 days a week · 4 days a week · 37.5 vs 40 hours · part-time hours tables · days vs hours · examples by days per week
Frequently asked questions
What is 22.5 hours pro rata of 37.5?
22.5 ÷ 37.5 = 0.6, so the employee works 60% of full time.
What is 30 hours as an FTE?
It depends on the employer’s full-time week. Against 37.5 hours it is 0.8 FTE; against 40 hours it is 0.75 FTE.
Does fewer days always mean lower FTE?
No. Compressed-hours staff may work full-time hours across fewer days and remain 1.0 FTE.
Can pro rata hours be used for salary and holiday?
The ratio can help, but statutory holiday rules and contractual benefits should be checked separately.
Authoritative sources
This article is general information, not personalised legal, tax or payroll advice. Employment contracts, collective agreements and individual circumstances can change the correct result.