Working out pro rata pay means calculating a part-time salary as a proportional share of the equivalent full-time wage. The core formula divides your actual contracted hours by the full-time hours, then multiplies by the full-time annual salary. For example, 22.5 hours across a 37.5-hour full-time week gives a 60% ratio — so a £35,000 FTE role becomes £21,000 pro rata. The same logic applies to holiday entitlement, pension, and sick pay.
The Pro Rata Pay Calculation Formula
Before reaching for a calculator, it helps to understand what the formula is actually doing — because once you see the logic, you can apply it to any working pattern or salary figure.
The standard pro rata pay calculation formula is:
Pro Rata Salary = FTE Salary × (Your Hours ÷ Full-Time Hours)
That’s it. Two numbers divided to create a ratio, then multiplied by the full-time salary. Every pro rata calculation — whether it’s for hours, days, or weeks — works from this same principle.
Hours-based example:
- FTE salary: £42,000
- Full-time hours: 37.5 per week
- Your hours: 30 per week
- Ratio: 30 ÷ 37.5 = 0.8 (80%)
- Pro rata salary: £42,000 × 0.8 = £33,600
Days-based example:
- FTE salary: £28,000
- Full-time days: 5 per week
- Your days: 3 per week
- Ratio: 3 ÷ 5 = 0.6 (60%)
- Pro rata salary: £28,000 × 0.6 = £16,800
Use hours when your contract specifies a weekly hours total. Use days when you work consistent full days and your contract is written that way. Both give identical results when daily hours are uniform.
Step-by-Step: How to Work Out Pro Rata Pay
Step 1 — Find the Full-Time Equivalent Salary
The FTE salary is the annual amount the role would pay at full-time hours. For new job offers, this is usually the salary figure shown in the advert. For existing employees moving to part-time, it’s the salary written in the original contract.
Never guess the FTE salary. If the advert says “£32,000 pro rata”, that £32,000 is the FTE figure — your actual salary will be lower once the hours ratio is applied.
Step 2 — Confirm the Full-Time Hours for That Role
This is where many calculations go wrong. Different employers use different full-time hours:
- 37.5 hours — most common in office and professional roles
- 40 hours — common in manufacturing, retail, and some public sector roles
- 35 hours — used by some financial services employers
- 36 hours — some NHS and local authority contracts
Always use your employer’s contractual full-time hours — not a round number you assume. A 5-hour difference in what you define as “full-time” creates a meaningful difference in the pro rata result.
Step 3 — Calculate Your Hours Ratio
Divide your actual weekly hours by the full-time weekly hours. This gives you a decimal between 0 and 1 — your working fraction.
| Your Hours | Full-Time Hours | Ratio | Percentage |
| 37.5 | 37.5 | 1.0 | 100% (full-time) |
| 30 | 37.5 | 0.80 | 80% |
| 25 | 37.5 | 0.667 | 66.7% |
| 22.5 | 37.5 | 0.60 | 60% |
| 20 | 37.5 | 0.533 | 53.3% |
| 18.75 | 37.5 | 0.50 | 50% |
| 15 | 37.5 | 0.40 | 40% |
Step 4 — Multiply by the FTE Salary
Multiply the FTE salary by your ratio. The result is your pro rata annual gross salary.
Example in full:
- FTE salary: £45,000
- Your hours: 25 per week, full-time is 37.5
- Ratio: 25 ÷ 37.5 = 0.667
- Pro rata annual salary: £45,000 × 0.667 = £30,000
Step 5 — Break It Down Into Monthly, Weekly, and Hourly
Once you have the annual pro rata salary, the remaining breakdowns are simple:
- Monthly: Annual ÷ 12
- Weekly: Annual ÷ 52
- Daily: Annual ÷ 52 ÷ days worked per week
- Hourly: Annual ÷ 52 ÷ hours worked per week
Using the £30,000 example above (25 hours per week):
- Monthly: £30,000 ÷ 12 = £2,500
- Weekly: £30,000 ÷ 52 = £576.92
- Hourly: £30,000 ÷ 52 ÷ 25 = £23.08
The pro rata salary calculator handles all of this automatically — including income tax, National Insurance, and student loan deductions for the 2026/27 tax year — so you see the take-home figure, not just the gross.
The Alternative Method: Working Backwards from Hourly Rate
Some people find it easier to work from an hourly rate, particularly when comparing part-time jobs that are advertised at different hours.
Step 1: Calculate the FTE hourly rate
FTE Annual Salary ÷ 52 ÷ Full-Time Weekly Hours
Step 2: Calculate pro rata annual salary from hourly rate
Hourly Rate × Your Weekly Hours × 52
Example:
- FTE salary: £36,400 over 37.5 hours per week
- FTE hourly rate: £36,400 ÷ 52 ÷ 37.5 = £18.67/hour
- Your hours: 22.5 per week
- Pro rata annual salary: £18.67 × 22.5 × 52 = £21,840
Both methods produce the same result. The hourly rate method is particularly useful when checking whether a part-time offer is paying the same hourly rate as the full-time equivalent — which is a legal requirement under the Part-Time Workers (Prevention of Less Favourable Treatment) Regulations 2000.
How to Work Out Pro Rata Holiday Pay
Holiday entitlement scales by exactly the same logic as salary. Under the Working Time Regulations 1998, every UK worker is entitled to a minimum of 5.6 weeks’ paid annual leave. For a five-day week, that’s 28 days. For a part-time worker, it’s 5.6 multiplied by their actual working days per week.
Pro Rata Holiday = 5.6 weeks × Days Worked Per Week
| Days Per Week | Annual Leave Entitlement | Includes Bank Holidays |
| 5 days | 28 days | 8 bank holidays + 20 flexible days |
| 4 days | 22.4 days | 6.4 bank holidays + 16 flexible days |
| 3 days | 16.8 days | 4.8 bank holidays + 12 flexible days |
| 2.5 days | 14 days | 4 bank holidays + 10 flexible days |
| 2 days | 11.2 days | 3.2 bank holidays + 8 flexible days |
The Bank Holiday Problem Many Employers Get Wrong
This is one of the most misunderstood areas of pro rata holiday pay calculation, and it catches both employers and employees out.
Part-time workers are entitled to a proportional share of bank holidays — not the specific bank holidays that fall on their working days. England and Wales have 8 bank holidays per year. A three-day-week worker’s pro rata share is (3 ÷ 5) × 8 = 4.8 bank holiday days.
Here’s the issue: if a part-time worker’s contracted days are Monday, Tuesday, and Wednesday, and all 8 bank holidays fall on Monday and Friday — they can’t receive zero bank holiday days. They’re owed 4.8 days regardless. The cleanest employer solution is to build the bank holiday entitlement into the total holiday pot rather than managing it as separate days, giving a three-day-week worker 16.8 days total from which bank holidays are drawn.
GOV.UK guidance on holiday entitlement confirms that part-time workers must not be treated less favourably than full-time staff on leave allocation — making this a legal matter, not just an HR preference.
Pro Rata for Term-Time and Part-Year Workers
Term-time contracts — used widely for teaching assistants, school support staff, catering workers, and after-school club staff — require a second fraction in the calculation.
Pro Rata Salary = FTE Salary × (Your Hours ÷ FTE Hours) × (Weeks Worked ÷ 52)
Teaching assistant example:
- FTE salary for the role: £26,000
- Full-time hours: 37.5 per week
- Contracted hours: 32.5 per week
- Weeks worked per year: 39 (term-time only)
Calculation:
- Hours ratio: 32.5 ÷ 37.5 = 0.867
- Weeks ratio: 39 ÷ 52 = 0.75
- Pro rata salary: £26,000 × 0.867 × 0.75 = £16,905
The £16,905 is paid across 52 weeks as a monthly salary, even though the actual work happens over 39 weeks. This is standard practice — it averages the earnings so the worker receives consistent monthly pay rather than nothing in school holidays.
Holiday entitlement for term-time workers is already embedded in the contract in most cases, since the school holidays themselves function as the paid leave. If you’re unsure whether your contract handles this correctly, the ACAS guidance on term-time working arrangements provides a clear framework to check against.
Real-World Pro Rata Pay Examples Across UK Salary Levels
The table below shows pro rata gross salary across common FTE figures and working patterns. These figures are annual gross — take-home will be lower after income tax and National Insurance at 2026/27 rates.
| FTE Salary | 4 days (80%) | 3 days (60%) | 2.5 days (50%) | 22.5hrs/37.5hr week (60%) |
| £20,000 | £16,000 | £12,000 | £10,000 | £12,000 |
| £25,000 | £20,000 | £15,000 | £12,500 | £15,000 |
| £30,000 | £24,000 | £18,000 | £15,000 | £18,000 |
| £35,000 | £28,000 | £21,000 | £17,500 | £21,000 |
| £40,000 | £32,000 | £24,000 | £20,000 | £24,000 |
| £50,000 | £40,000 | £30,000 | £25,000 | £30,000 |
| £60,000 | £48,000 | £36,000 | £30,000 | £36,000 |
For take-home pay including income tax, NI, and student loan deductions at 2026/27 HMRC rates, use the pro rata salary calculator to run your specific figures.
What Pro Rata Means for Statutory Sick Pay
Statutory Sick Pay works slightly differently to salary under pro rata rules. SSP for 2026/27 is £123.25 per week — this figure does not get reduced proportionally for part-time workers. However, it is only paid for qualifying days, meaning the days the employee is actually contracted to work.
A three-day-week employee off sick for a full week receives SSP for three qualifying days. The daily SSP rate therefore appears higher for a part-time worker than a full-time one — same weekly pot, fewer qualifying days.
The exception: if a part-time worker earns less than the SSP weekly rate (unlikely above minimum wage, but possible for very low-hours workers), they receive 80% of their average weekly earnings rather than the flat SSP rate.
How to Check Whether Your Pro Rata Salary Is Correct
If your pay doesn’t feel right, this four-step check takes about two minutes:
- Find the FTE salary for your role — it should be stated in your original job advert or contract.
- Divide your contracted hours by the full-time hours for that role (check your contract for both figures).
- Multiply the FTE salary by that ratio.
- Compare to your actual gross salary on your payslip. If there’s a material difference, raise it in writing with your HR department.
Underpayment isn’t always deliberate — the most common employer errors are using the wrong full-time hours figure (40 instead of the contractual 37.5, for instance), or failing to update salary when a working pattern changes.
If you’ve raised the issue internally without resolution, ACAS offers free early conciliation before any employment tribunal claim, and their pay dispute guidance walks through the process clearly.
For employers: always verify the hourly rate against the National Minimum Wage floor. For 2026/27, the NMW is £12.71/hour for workers aged 21 and over, and £10.85/hour for 18–20-year-olds. A pro rata calculation that lands below these thresholds is unlawful regardless of the FTE salary it was derived from.
Salary Sacrifice and Pro Rata: What Changes
If an employee joins a salary sacrifice scheme — cycle to work, childcare vouchers, electric vehicle leasing, or additional pension contributions — the gross salary figure used for the scheme deduction is the pro rata salary, not the FTE.
This matters because salary sacrifice reduces the gross figure used for income tax and NI calculations. On a reduced pro rata salary, some workers find that salary sacrifice brings them close to or below the personal allowance (£12,570 for 2026/27) or below the NI Primary Threshold (£12,570 annually). This can affect:
- Student loan repayment thresholds
- State Pension qualifying earnings (Lower Earnings Limit: £6,396 for 2026/27)
- Mortgage affordability calculations that use gross income
In practice, this doesn’t affect most part-time workers at mid-range salaries, but it’s worth checking if you’re working very reduced hours.
Part-Time Salary Negotiation: Using Pro Rata Calculations to Your Advantage
When moving from full-time to part-time — or accepting a part-time role — the pro rata figure gives you a concrete basis for negotiation. A few things worth knowing before the conversation:
The advert is the baseline. If a job is advertised at £40,000 FTE and you’re offered four days a week, you should expect £32,000. If the employer offers less, you have grounds to negotiate back to the proportional figure.
Hours creep is common. Part-time roles sometimes involve the same workload as the full-time version, just compressed. If your actual hours regularly exceed your contracted hours, the effective hourly rate decreases. Documenting this gives you grounds to either renegotiate hours or adjust the salary.
Benefits don’t always scale neatly. Some employers offer benefits — gym membership, private healthcare, professional subscriptions — that don’t reduce pro rata. Others cap them. Check the terms for each benefit individually rather than assuming they scale with salary.
The complete UK guide to pro rata salary covers employer obligations in more detail if you’re preparing for that conversation.
Frequently Asked Questions
How do I calculate my pro rata pay?
Divide your contracted weekly hours by the full-time weekly hours for the role. Multiply the resulting fraction by the annual FTE salary. If you work 25 hours out of a 37.5-hour full-time week, your ratio is 0.667 — so a £36,000 FTE role gives you £24,000 pro rata. For take-home pay after tax, use a UK pro rata salary calculator with 2026/27 HMRC rates applied.
How to calculate a pro rata amount for partial-year working?
For term-time or seasonal workers, apply two fractions: hours ratio and weeks ratio. Multiply the FTE salary by (your hours ÷ full-time hours), then multiply that result by (weeks worked ÷ 52). A worker on £30,000 FTE working 37.5 hours over 39 weeks would earn £30,000 × 1.0 × (39 ÷ 52) = £22,500 pro rata annually.
How is pro rata salary calculated when days are used instead of hours?
Divide your working days per week by the employer’s full-time days per week, then multiply by the FTE salary. Three days out of five is 0.6 — so £40,000 FTE becomes £24,000 pro rata. The result is identical to the hours method as long as your daily hours are consistent across your working days.
How to work out your pro rata if your hours vary week to week?
Use an average weekly hours figure, ideally based on the contracted minimum or a 12-week reference period. HMRC’s guidance on variable-hours workers recommends using the average hours over the 12 weeks immediately before the calculation date. This is particularly relevant for zero-hours contracts and annualised hours arrangements.
How do they calculate pro rata holiday pay?
Multiply 5.6 weeks by the number of days you work per week. Someone working three days a week gets 5.6 × 3 = 16.8 days annual leave. For workers on irregular hours, the holiday pay calculation uses an average of earnings over a 52-week reference period under the Employment Rights (Amendment) Regulations 2023, which updated the rules for variable-pay workers.
What is an example of pro rata pay in practice?
A marketing manager role is advertised at £48,000 FTE for 37.5 hours per week. The candidate agrees to work 30 hours per week (four days). Their pro rata salary is £48,000 × (30 ÷ 37.5) = £38,400 gross per year. Monthly gross: £3,200. After income tax and NI at 2026/27 rates, estimated monthly take-home is approximately £2,660.
What is the pro rata rule in employment law?
The pro rata principle in UK employment law means part-time workers must receive the same terms and conditions as comparable full-time workers, scaled proportionally to their hours. This is established in the Part-Time Workers (Prevention of Less Favourable Treatment) Regulations 2000, which covers pay, holiday, pension access, training, and career development opportunities — not just the headline salary figure.
What is the formula for pro rata sick pay?
Statutory Sick Pay is £123.25 per week (2026/27) and is not reduced pro rata. However, it only applies to qualifying days — your contracted working days. A part-time worker on a three-day week receives SSP for three qualifying days per week of illness. Contractual sick pay schemes vary by employer and may be calculated pro rata depending on the policy wording.
How is pro rata pay actually paid — monthly or weekly?
Pro rata salary is almost always paid monthly in salaried roles, regardless of the working pattern. The annual pro rata gross is divided by 12, and that monthly amount appears on the payslip. Even term-time workers who only work 39 weeks per year typically receive 12 equal monthly payments across the full year for financial predictability.
How do we calculate pro rata for a mid-year salary change?
If an employee changes their hours part-way through the year, calculate how much of the year was spent at each rate. For a change in October (week 27 of 52), pay 26 weeks at the old rate and 26 weeks at the new rate, prorated accordingly. Payroll software handles this automatically, but verifying the payslip figures against manual calculations is good practice whenever a contract changes.