What Does Pro Rata Mean? How to Calculate Your Pro Rata Salary

A job advert offers a salary of £40,000 pro rata. You will work three days a week.

Are you earning £40,000?

No. In most job adverts, £40,000 is the salary someone would receive for working the full time hours attached to the role. Your actual salary is reduced in proportion to the hours or days you work.

For a three day week where the full time role is five days, £40,000 becomes £24,000 a year.

That is the basic idea behind pro rata pay.

Pro rata means in proportion. In employment, it is commonly used to adjust salary, holiday entitlement, bonuses and some other benefits according to how much someone works compared with a full time employee.

Acas describes pro rata as giving pay and leave in proportion to hours worked. It gives the example of a full time employee earning £28,000 and someone doing half the hours earning £14,000.

You will see the term most often in part time job adverts:

Salary: £35,000 pro rata

This usually means £35,000 is the full time equivalent salary, sometimes shortened to FTE. Your actual gross salary depends on the proportion of the full time hours you will work.

It is worth checking the wording. A salary shown as simply £35,000 per year is different from £35,000 pro rata if the position is part time.

The most reliable calculation is usually based on weekly hours:

Full time salary × your weekly hours ÷ full time weekly hours

Suppose the full time salary is £42,000 and the organisation considers 37.5 hours a full working week.

You are contracted for 22.5 hours.

£42,000 × 22.5 ÷ 37.5 = £25,200

Your pro rata salary is therefore £25,200 a year before tax and other deductions.

The 22.5 hour contract is 60% of the full time working week, so you receive 60% of the full time salary.

If you are paid monthly:

£25,200 ÷ 12 = £2,100 gross per month

That is the figure from which Income Tax, National Insurance, pension contributions, student loan repayments and any other payroll deductions would normally be calculated.

If everyone works days of the same length, you can often use days instead.

For a £45,000 full time salary and a five day working week:

So someone working three days receives:

£45,000 × 3 ÷ 5 = £27,000

Hours are normally a better basis when working days have different lengths. Someone working three ten hour days, for example, is not necessarily equivalent to someone working three seven hour days.

This is one of the easiest points to miss when reading a job advert.

Imagine a vacancy says:

Salary: £30,000 pro rata

Hours: 24 hours per week

Full time hours: 40 hours per week

Your working percentage is:

24 ÷ 40 = 60%

The salary you would actually receive is:

£30,000 × 60% = £18,000 a year

Your gross monthly salary would be £1,500.

The £30,000 figure is useful because it allows salaries to be compared on the same full time basis. But if you are budgeting around a new job, £18,000 is the figure that matters.

If you are genuinely paid by the hour, there may be no need to calculate a pro rata annual salary. Your earnings are simply based on the hours for which you are paid.

You can still convert the rate into an approximate annual figure.

Someone earning £16 an hour for 25 hours a week would earn:

£16 × 25 × 52 = £20,800

That assumes 52 paid weeks at the same hours. The real figure can differ for workers whose hours change, who have unpaid periods, or whose employment arrangements deal with holiday pay differently.

Salary and hourly pay should also be checked against National Minimum Wage rules. From 1 April 2026, the National Living Wage for workers aged 21 and over is £12.71 an hour. Different statutory rates apply to younger workers and qualifying apprentices.

A salary being described as pro rata does not remove those minimum pay requirements.

Part time work is the obvious example, but the same principle can appear elsewhere.

Someone might join an employer halfway through a bonus period and receive part of the annual bonus. A worker starting part way through an employer's holiday year might receive only the proportion of annual leave that relates to the remainder of that year. Someone leaving during the year can also have entitlements calculated according to the portion of the year worked.

The calculation therefore depends on what is being divided.

For salary, the comparison is often working hours.

For annual leave, it might be working days or hours.

For a yearly allowance, it might be months or calendar days.

For a bonus, the scheme rules might use time employed, contracted hours, performance, or a mixture of factors.

This is why the words pro rata alone do not always tell you the exact amount. The contract or policy should explain what the employer is using as the basis of the calculation.

Holiday is another common place where pro rata calculations matter.

Almost all workers in the UK are legally entitled to 5.6 weeks of paid holiday each year. Someone working five days a week will normally receive at least 28 days. Someone regularly working three days a week is entitled to at least:

3 × 5.6 = 16.8 days

Someone working four days receives at least:

4 × 5.6 = 22.4 days

GOV.UK confirms that part time workers working regular hours throughout the year still receive 5.6 weeks of statutory leave, although this translates into fewer days than for someone working five days a week.

Employers can provide more generous holiday allowances.

If a company gives full time employees 30 days of annual leave and you work 60% of the full time hours, your contractual entitlement might be calculated as:

30 × 60% = 18 days

The precise calculation may depend on whether leave is recorded in days or hours and how the working pattern is arranged.

Bank holidays can also form part of statutory annual leave. They do not automatically have to be given as additional paid days on top of the statutory entitlement.

Irregular hours and part year workers have specific rules. For leave years beginning on or after 1 April 2024, statutory holiday entitlement for these workers is generally accrued at 12.07% of hours worked during a pay period.

That makes a simple days per week calculation unsuitable for some contracts.

Working part time does not mean an employer can simply exclude someone from employment benefits because they work fewer hours.

UK rules protect part time workers against being treated less favourably than comparable full time workers solely because they are part time. This protection can apply to areas including pay, pensions, holidays, training and career development.

Some benefits can still be provided on a pro rata basis.

For example, if a full time employee receives a £1,200 annual benefit and someone works 50% of the full time hours, the equivalent pro rata amount could be £600.

Not everything has to be divided automatically. The details depend on the benefit and the employment terms. A company might provide the same private medical insurance to every eligible employee, for example, rather than reducing its value according to working hours.

Bonus schemes can also have their own rules. Check whether a bonus is based on full time equivalent salary, actual salary, time worked during the bonus year or individual performance.

If your gross salary falls from £40,000 to £20,000 because you move from full time hours to 50% hours, you should not assume your take home pay will also fall by exactly 50%.

Income Tax works through allowances and tax bands rather than taking the same percentage from every pound earned.

For the 2026 to 2027 tax year, the standard Personal Allowance is £12,570. For most taxpayers in England, Wales and Northern Ireland, employment income above the allowance then enters the relevant Income Tax bands. Scotland has different Income Tax bands.

As a result, cutting a gross salary in half can reduce Income Tax by more than half in some situations.

National Insurance, pension contributions and student loan repayments can also change with earnings.

The sensible order is therefore:

Calculate your gross pro rata salary first.

Then calculate the deductions that apply to that new salary.

Trying to calculate take home pay by simply multiplying your existing net salary by your working percentage can give the wrong answer.

This is another situation where the word pro rata appears, but the calculation can be different from part time salary calculations.

Suppose your normal annual salary is £36,000 but you start during a monthly payroll period. Your first payslip will usually contain only the salary relating to the part of that pay period for which you were employed.

There is not one universal calculation that every employer must use for every contractual salary. Payroll calculations can depend on the contract and the employer's payroll methodology, so it is worth checking how a daily rate has been calculated if the amount on your first or final payslip is unexpected.

Holiday entitlement is clearer in principle. Someone who starts part way through a leave year is generally entitled only to the proportion of their annual leave relating to the remaining part of that leave year. GOV.UK provides specific guidance and a holiday entitlement calculator for these situations.

Take the salary quoted in the advert and find the full time weekly hours for the role.

Then compare them with your contracted hours.

If the advert says £48,000 pro rata, with full time hours of 40 per week, and you will work 32:

32 ÷ 40 = 0.8

£48,000 × 0.8 = £38,400

Your gross salary should therefore be £38,400 a year, assuming the advertised figure really is the full time equivalent and there are no other contractual adjustments.

The same calculation works for most straightforward part time salaries:

Pro rata salary = full time salary × your hours ÷ full time hours

Once you know that figure, you can calculate monthly gross pay, estimate your tax and National Insurance, and compare the job properly with other offers rather than comparing two full time equivalent salaries that represent very different actual earnings.