If you work fewer hours than a full-time employee, your salary is usually adjusted according to your working pattern. A pro rata salary shows what you could earn compared with the full-time salary for the same role. This guide explains the pro rata salary calculation, how to calculate monthly pay, and how the formula applies to a pro rata salary UK arrangement. You can use proratacalculators to check your figures quickly with a Pro Rata Salary Calculator.

What Is Pro Rata Salary?

Pro rata salary is the amount a part-time employee earns in proportion to the full-time salary for the same job.

For example, if a full-time employee earns £40,000 for 40 hours per week and you work 20 hours, you work 50% of the full-time hours.

The calculation is:

£40,000 × 20 ÷ 40 = £20,000

Your estimated annual pro rata salary would therefore be £20,000 before tax and other deductions.

The calculation is based on the full-time salary and the number of hours or days you work.

How to Calculate Pro Rata Salary

If you want to know how to calculate pro rata salary, use this basic formula:

Pro Rata Salary = Full-Time Salary × Part-Time Hours ÷ Full-Time Hours

For example:

• Full-time salary: £36,000

• Full-time hours: 40 hours

• Part-time hours: 24 hours

Calculation:

£36,000 × 24 ÷ 40 = £21,600

The estimated annual salary is £21,600.

You can also calculate the percentage of full-time hours first:

24 ÷ 40 × 100 = 60%

You are working 60% of the full-time schedule, so you receive 60% of the full-time salary.

How Does a Part-Time Salary Work?

A part-time salary is normally based on the proportion of full-time hours worked.

For example, a full-time employee works 37.5 hours per week and earns £37,500 annually. If you work 22.5 hours, you work 60% of the full-time hours.

The calculation is:

£37,500 × 22.5 ÷ 37.5 = £22,500

Your estimated annual part-time salary is £22,500.

UK guidance states that part-time workers should generally receive at least the same hourly pay rate as comparable full-time workers.

Pro Rata Salary Calculation by Days

You can calculate salary using working days when your contract is based on days rather than hours.

Suppose the full-time salary is £30,000 and a full-time employee works five days per week. If you work three days per week:

£30,000 × 3 ÷ 5 = £18,000

Your estimated annual salary is £18,000.

Use the working pattern stated in your contract. If your daily hours vary, an hourly calculation may be more appropriate.

Pro Rata Salary UK Example

For a simple pro rata salary UK calculation, consider a job advertised at £42,000 for 40 hours per week.

If you work 30 hours:

£42,000 × 30 ÷ 40 = £31,500

Your annual gross salary would be £31,500.

To estimate your monthly gross salary:

£31,500 ÷ 12 = £2,625

This is your gross monthly figure before applicable deductions.

Your actual take-home pay can be lower because your payslip may include deductions such as Income Tax, National Insurance, pension contributions, or other authorised deductions. GOV.UK explains that payslips show earnings before and after deductions.

How to Calculate Monthly Pro Rata Salary

If you already know your annual pro rata salary, divide it by 12 to estimate monthly gross pay.

For example:

Annual salary: £24,000

£24,000 ÷ 12 = £2,000

Your estimated monthly salary is £2,000.

If your salary is paid monthly and your working hours remain the same throughout the year, this gives you a straightforward monthly estimate.

What Is a Part-Month Salary?

A part-month salary is pay for only part of a monthly pay period.

This can happen when you start a job after the beginning of the month or leave before the month ends.

For example, an employee with a monthly salary may work only part of their first month. The employer then needs to calculate the amount due for that shortened period.

The exact part-month salary calculation can depend on the employer's payroll method, contract, and the number of days or hours involved. HMRC guidance also recognises pro rata calculators for shortened pay periods when employment starts part way through a pay period.

Therefore, do not assume that working half a month always means receiving exactly half of the monthly salary.

Pro Rata Salary for Part-Time Workers

Pro rata salary for part-time workers is useful when comparing different working arrangements.

For example:

Full-time salary: £35,000
Full-time hours: 35 per week
Part-time hours: 21 per week

Calculation:

£35,000 × 21 ÷ 35 = £21,000

The employee works 60% of the full-time hours and receives an estimated annual salary of £21,000.

This calculation can help when comparing a full-time job with a reduced-hours position.

Does Pro Rata Salary Include Holiday Pay?

Pro rata salary and holiday entitlement are related but should not be treated as the same calculation.

Part-time workers are generally entitled to paid holiday, and entitlement can be calculated according to their working pattern. GOV.UK states that most workers are entitled to 5.6 weeks of paid holiday each year, with specific calculation methods depending on working hours.

If you work irregular or part-year hours, holiday pay calculations can be more detailed and may use average pay over a reference period.

When Should You Use a Pro Rata Salary Calculator?

A Pro Rata Salary Calculator is useful when you need to:

• Calculate part-time annual salary

• Estimate monthly gross pay

• Compare different working hours

• Check a part-time job offer

• Calculate salary based on working days

• Compare full-time and part-time earnings

For a straightforward fixed-hours contract, you usually only need the full-time salary, full-time hours, and your contracted hours.

Simple Pro Rata Salary Example

Suppose your full-time salary is £32,000 and the full-time schedule is 40 hours per week.

You work 25 hours.

First calculate the working percentage:

25 ÷ 40 = 62.5%

Then calculate your salary:

£32,000 × 62.5% = £20,000

Your estimated annual pro rata salary is £20,000.

Your estimated monthly gross salary is:

£20,000 ÷ 12 = £1,666.67

This example assumes the salary is directly proportional to the contracted hours.

Final Thoughts

The basic pro rata salary formula is:

Full-Time Salary × Part-Time Hours ÷ Full-Time Hours

If the full-time salary is £40,000 for 40 hours and you work 20 hours, your estimated annual salary is £20,000.

A Pro Rata Salary Calculator makes this calculation faster and helps you compare different working patterns. For unusual schedules, variable hours, bonuses, or specific payroll calculations, check your employment contract and employer's calculation method.

1. What is pro rata salary?

Pro rata salary is pay calculated in proportion to the full-time salary based on your contracted working hours or days.

2. How do I calculate pro rata salary?

Multiply the full-time salary by your part-time hours and divide by the full-time hours.

3. Is pro rata salary gross or net?

It normally refers to gross salary before tax, National Insurance, pension contributions, and other deductions.

4. Can I calculate salary by working days?

Yes. Divide your working days by the full-time working days and multiply the result by the full-time salary.

5. Can I calculate monthly pro rata pay?

Yes. Calculate your annual pro rata salary first, then divide it by 12 for an estimated monthly gross salary.