What is Pro Rata Basis
Understanding what is pro rata basis in the UK workplace
What Does "Pro Rata Basis" Mean?
A pro rata basis is a method of calculation where amounts are divided or allocated proportionally according to a specific factor — usually time, hours, or usage. In UK employment, "on a pro rata basis" means benefits and entitlements are scaled in proportion to actual working hours compared to full-time equivalents.
The concept applies universally: council tax bills for part-year residents, insurance premiums for mid-year policies, dividend payments for partial shareholding periods, and utility bills for shared occupancy all use pro rata basis calculations.
Pro Rata Basis in Employment
When your employer says holiday is "calculated on a pro rata basis," they mean your entitlement is proportional to your hours. The statutory formula is straightforward:
| Benefit | Full-Time | 0.6 FTE (3 days) | 0.4 FTE (2 days) |
|---|---|---|---|
| Salary (£30k FTE) | £30,000 | £18,000 | £12,000 |
| Holiday (28 days) | 28 days | 16.8 days | 11.2 days |
| Sick pay | Full rate | 60% rate | 40% rate |
| Training budget (£500) | £500 | £300 | £200 |
Beyond Employment: Pro Rata in Everyday Life
Pro rata basis calculations appear in many financial contexts: mortgage interest calculations when overpaying mid-month, annual subscriptions refunded partway through, rent adjustments for partial months, and energy bills estimated between meter readings. The maths is always identical — divide the total by the full period, then multiply by your actual period.
For employment-specific calculations, use our pro rata calculator. See also pro rata meaning UK for the legal framework, or pro rata charges for billing contexts.
Quick Summary: What is Pro Rata Basis
If you're short on time, here's what you need to know about what is pro rata basis:
- What it means: What is Pro Rata Basis refers to proportional calculation 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: What is Pro Rata Basis
Let's work through a practical example of what is pro rata basis. 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 What is Pro Rata Basis
- 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 what is pro rata basis, 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.