How to Calculate Pro Rata Salary
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The Complete Guide to Calculating Pro Rata Salary
Learning how to calculate pro rata salary is essential whether you're evaluating a job offer, switching to part-time, or verifying your payslip. This guide covers the standard UK method used by payroll departments nationwide, plus advanced scenarios like term-time adjustments and mid-month starts.
The core principle is simple: you earn the same hourly rate as a full-time employee in the same role, but your total pay reflects only the hours you actually work.
The Standard UK Calculation Method
1. Identify the FTE salary
This is the annual salary for the role at full-time hours. It appears on job adverts and your contract, usually followed by "pro rata" if the role is part-time.
2. Confirm full-time hours
Ask HR for the standard full-time hours. Common figures: 35h (some civil service), 37.5h (NHS, most employers), 40h (some private sector).
3. Note your contracted hours
Your employment contract states your weekly hours. If you work variable hours, use the average over a 12-week reference period.
4. Apply the formula
Multiply: FTE Salary × (Your Hours ÷ FT Hours). The result is your gross annual pro rata salary before tax deductions.
Advanced Scenarios
Mid-year start: If you join partway through the year, your first year's salary is further pro-rated by the number of remaining days. Example: starting 1 October means 6/12 of your annual pro rata figure.
Term-time workers: School staff need a double pro rata — once for hours, once for weeks. Use our term-time calculator for accurate figures.
Overtime: Pro rata salary covers contracted hours only. Any additional hours may attract overtime rates — check with our overtime calculator.
How to Use the How to Calculate Pro Rata Salary
Using our how to calculate pro rata salary is straightforward. Follow these steps to get accurate results for your situation:
- Enter your full-time salary — This is the annual salary for the equivalent full-time role, before any deductions. You'll find this on the job advert or your contract.
- Set the full-time hours — The standard working week for the role. Most UK employers use 37.5 or 40 hours per week.
- Enter your actual hours — Your contracted weekly hours. This is the number you actually work.
- Click Calculate — The how to calculate pro rata salary displays your results instantly, with annual, monthly, weekly, daily, and hourly breakdowns.
Worked Example: How to Calculate Pro Rata Salary
Let's work through a practical example of how to calculate pro rata salary. 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 Using This Calculator
- 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.
Related Salary Calculators
Our how to calculate pro rata salary is just one of the tools available on ProRataCalculator. 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.