How to Calculate Pro Rata Salary in the UK: A Guide for Part-Time and Term-Time Workers

How to Calculate Pro Rata Salary in the UK

If you work part-time or term-time hours, your salary is usually scaled down from a full-time equivalent (FTE) figure. This is called a pro rata salary — meaning "in proportion" to the hours or weeks you actually work. Knowing how to calculate pro rata salary helps you compare job offers accurately and understand what your take-home pay will be.

This guide explains the formula, how tax and National Insurance apply, and gives real-world examples based on 2026/27 rates. We’ll also cover pensions and student loans, and point you to a take-home calculator to see your own net pay.

The Basic Pro Rata Formula

The standard method is straightforward:

Pro rata salary = (your contracted hours ÷ full-time hours) × full-time salary

For example, if the FTE role pays £35,000 for 37.5 hours per week, and you work 22.5 hours, your pro rata salary is:

22.5 ÷ 37.5 × £35,000 = £21,000 per year.

This is the gross figure before any deductions. Your actual pay is then taxed in the same way as any other salary of that size. The same formula works for term-time only roles, as explained below.

What Counts as ‘Full-Time’?

Most UK employers define full-time as 35–40 hours per week (often 37.5 in the NHS or 35 in local government). For days, a full-time week is usually 5 days. The formula uses whatever the employer considers standard for the role. Always check the contract or job advert for the FTE hours or days.

Term-Time Working

School staff and some public sector roles work a full week during term time but are unpaid over holidays. The calculation then uses weeks per year instead of (or alongside) hours per week:

Pro rata salary = (weeks worked ÷ 52) × (days per week ÷ 5) × FTE salary

For instance, a teacher on a £30,000 FTE working 39 weeks a year, 5 days a week:

39/52 × 5/5 × £30,000 = 0.75 × £30,000 = £22,500.

Never try to squeeze term-time patterns into a ‘days per week’ field alone — that would give a misleading result. Use a calculator that accounts for both fractions, like the one on After Tax Salary.

How Tax and National Insurance Work on Pro Rata

Once you have your pro rata gross salary, the next step is to work out deductions. The key principle is that the Personal Allowance is not pro-rated. For 2026/27, everyone gets a tax-free allowance of £12,570, regardless of how many hours or days they work. This means part-time workers often pay proportionally less tax than full-time colleagues.

Income Tax (for England, Wales, and Northern Ireland)

After the Personal Allowance, the following bands apply:

• Basic rate 20%: £12,571 to £50,270
• Higher rate 40%: £50,271 to £125,140
• Additional rate 45%: above £125,140

Only the income within each band is taxed at that rate. If you earn £27,000 pro rata (from a £45,000 FTE), you pay:

• 20% on £27,000 - £12,570 = £14,430 → £2,886 Income Tax.

Compare this to the full-time £45,000: 20% on £37,430 = £7,486 (but higher rate kicks in above £50,270). So the part-time worker saves a significant amount in tax.

National Insurance (Class 1)

Employee NI for 2026/27:

• 8% on earnings between £12,570 and £50,270
• 2% on earnings above £50,270

NI is charged per pay period, not cumulatively. On a £27,000 pro rata salary, you pay 8% on £14,430 = £1,154.40 per year. Take-home pay would be roughly £1,873 per month after both deductions, as shown in the salary data section.

Scotland

Scottish taxpayers have different Income Tax bands (starter, basic, intermediate, higher, and top rates). If you live in Scotland, you need to use Scottish rates for your income. The Personal Allowance is the same, but the thresholds and rates vary. Online calculators often have a toggle for Scottish taxpayers.

Example Pro Rata Take-Home Comparisons

Let’s look at a real comparison for 2026/27 (assuming no pension, no student loan, standard tax code 1257L):

	Full-time (37.5 hrs)	Part-time (22.5 hrs)
FTE salary	£45,000	£45,000
Pro rata salary	£45,000	£27,000
Income Tax	£6,486	£2,886
National Insurance	£3,294	£1,154
Annual net pay	£35,220	£22,960
Monthly take-home	£2,935	£1,913
Effective tax rate	21.7%	16.7%

The part-time worker keeps a higher percentage of their gross pay because more of their income falls within the tax-free allowance.

Other Deductions to Consider

Pension Contributions

Under auto-enrolment, the minimum total contribution is 8% of qualifying earnings (£6,240 to £50,270). Employees typically pay 5% (with basic-rate tax relief) and employers 3%. Your pension is deducted from your pro rata gross salary before Income Tax, so it reduces your taxable income. A £27,000 pro rata salary with 5% employee contribution would see about £1,350 deducted annually, but this costs roughly £1,080 in net pay (for a basic-rate taxpayer) because of tax relief.

Student Loan (Plan 1, 2, 4 and Postgraduate)

If you have a student loan, repayments depend on your gross earnings above the relevant threshold. These are not pro-rated — they apply to your actual pro rata salary. For 2026/27, Plan 2 threshold is about £27,295 per year, so someone earning £27,000 would not repay unless above that threshold. Check your plan with HMRC.

Using an Online Calculator

Manual calculations are fine for rough estimates, but for precise net pay, use a take-home calculator that handles all edge cases: Scottish bands, pension sacrifice, student loan plans, and term-time patterns. The calculator on this site uses the latest HMRC rates and thresholds for 2026/27.

Frequently Asked Questions

Do I pay less tax on a pro rata salary?

Yes, because your gross salary is lower. However, the Personal Allowance of £12,570 for 2026/27 is not reduced for part-time workers. You still receive the full tax-free amount, meaning a smaller proportion of your income falls into taxable bands. For example, a £27,000 pro rata salary from a £45,000 FTE role attracts about £2,886 in Income Tax (after PAYE), compared to £6,486 if you worked full-time.

How is a term-time only salary calculated?

Term-time roles (common in schools and some public sector jobs) are calculated using the weeks-per-year fraction instead of the days-per-week fraction. The formula is: (weeks worked ÷ 52) × (days per week ÷ 5) × full-time salary. For example, working 39 weeks a year, 5 days a week on a £30,000 FTE gives 39/52 × 5/5 = 0.75, so £22,500 per year. This is then taxed and NI’d normally.

Does my pension affect take-home pay on a pro rata salary?

Yes. Under auto-enrolment, the minimum total contribution is 8% of qualifying earnings (£6,240 to £50,270). Employees typically pay 5% (with tax relief) and employers 3%. Your pension contributions are deducted from gross pay before Income Tax, so a £1 contribution reduces your net pay by about 80p for a basic-rate taxpayer. Salary sacrifice arrangements can save even more by also reducing National Insurance.