Pro Rata Salary Calculation
Clear explanation with practical examples for UK workers
Pro Rata Salary Calculation: Methods and Formulas
Pro rata salary calculation is the process of determining the correct pay for a worker who works fewer hours than the full-time standard. The UK uses a straightforward proportional method endorsed by CIPD, ACAS, and all major public sector frameworks. This page covers multiple calculation approaches so you can choose the one that suits your situation.
Three Methods, Same Result
Method A: Hours Ratio
Best for: Simple hour-for-hour calculations. Used by most private sector employers.
Method B: FTE Decimal
Best for: NHS, local government, and organisations that use FTE in HR systems.
Method C: Hourly Rate
Best for: Verifying payslip accuracy and comparing different roles.
When Standard Calculation Is Not Enough
Standard pro rata only adjusts for hours. Additional adjustments are needed for: Term-time workers — use our term-time calculator. Mid-year starters — pro rata the annual figure by months/days remaining. Variable hours — use a 12-week average of actual hours. Salary sacrifice — calculate pro rata first, then apply sacrifice deduction using our sacrifice calculator.
For the quickest calculation, use our pro rata calculator which handles all standard scenarios. For detailed step-by-step instructions, read how to calculate pro rata salary.
Quick Summary: Pro Rata Salary Calculation
If you're short on time, here's what you need to know about pro rata salary calculation:
- What it means: Pro Rata Salary Calculation involves calculating pay or entitlement proportionally based on the ratio of hours or time worked versus the full-time equivalent.
- The formula: Full-Time Amount × (Your Hours ÷ Full-Time Hours) = Your Pro Rata Amount
- Who needs it: Part-time workers, term-time staff, teachers, job-sharers, and anyone on reduced hours.
- UK law: Under the Part-time Workers Regulations 2000, part-time employees have the right to be treated no less favourably than comparable full-time workers.
Worked Example: Pro Rata Salary Calculation
Let's work through a practical example of pro rata salary calculation. A marketing coordinator role advertises a full-time salary of £28,000 for 37.5 hours per week. You're offered the position at 25 hours per week.
Step 1 — Find your FTE ratio: 25 ÷ 37.5 = 0.667 (66.7%)
Step 2 — Calculate pro rata salary: £28,000 × 0.667 = £18,667 per year
Step 3 — Monthly breakdown: £18,667 ÷ 12 = £1,556 gross per month
Step 4 — Holiday entitlement: 28 days × 0.667 = 18.7 days pro rata
After income tax and NI (2025/26 rates), your monthly take-home would be approximately £1,377. Use our pro rata calculator above to check your own figures.
Tips for Pro Rata Salary Calculation
- Always use gross salary: Enter the salary before tax and deductions — the calculator works with gross figures.
- Check your contract: Your employment contract should state your full-time equivalent hours. Common UK standards are 35, 37, 37.5, and 40 hours per week.
- Know your rights: Under the Part-time Workers Regulations 2000, part-time employees must receive the same hourly rate, holiday entitlement (pro rata), and benefits as full-time colleagues.
- Tax personal allowance: For 2025/26, the first £12,570 of earnings is tax-free. If your pro rata salary falls below this, you pay no income tax at all.
- National Insurance: Employee NI is 8% on earnings between £12,570 and £50,270 (2025/26 rates). Check HMRC NI rates for the latest figures.
Pro Rata Holiday Entitlement
Under the Working Time Regulations 1998, all UK workers are entitled to a minimum of 5.6 weeks' paid holiday per year (28 days for full-time). If you work part-time, your entitlement is calculated pro rata based on your actual hours or days worked.
| Days Worked/Week | FTE Ratio | Statutory Days/Year | Bank Holidays (pro rata) |
|---|---|---|---|
| 5 days (full-time) | 1.0 | 28 days | 8 days |
| 4 days/week | 0.8 | 22.4 days | 6.4 days |
| 3 days/week | 0.6 | 16.8 days | 4.8 days |
| 2.5 days/week | 0.5 | 14 days | 4 days |
| 2 days/week | 0.4 | 11.2 days | 3.2 days |
Holiday entitlement is always rounded up — never down — when the result is not a whole number, per ACAS guidance on holiday entitlement. Bank holidays may be included in or added on top of your statutory 28 days, depending on your contract.
All calculations on this page follow ACAS pro rata pay guidelines and are consistent with the UK Employment Rights Act 1996. Tax figures use HMRC 2025/26 rates. The April 2025 National Living Wage of £12.21/hour is applied where relevant.
Further Reading
For more help with pro rata salary calculation, explore our free UK tools. You may also find these useful: term-time salary calculator, overtime calculator, holiday pay guide.
Last updated: February 2026. Verified against HMRC 2025/26 tax rates and April 2025 National Living Wage (£12.21/hour).
Frequently Asked Questions
Pro rata means "in proportion." In employment, it refers to adjusting a full-time salary proportionally based on the number of hours, days, or weeks actually worked compared to a full-time equivalent role.
Divide the full-time salary by full-time hours, then multiply by your actual hours. For example: £30,000 ÷ 37.5 hours × 25 hours = £20,000 pro rata.
Pro rata salary is usually calculated before holiday pay. Your holiday entitlement is also pro-rated — part-time workers get 5.6 weeks holiday pro rata, calculated proportionally to hours worked.
Not exactly. Pro rata is the method used to calculate part-time salary. It ensures part-time workers receive the proportional equivalent of the full-time rate, maintaining fairness under UK employment law.