UK Pro-Rata Salary Calculator
Estimate your gross pro-rated pay based on hours and (optionally) a specific employment period.
How this prorated salary calculator UK works
A pro-rated salary is your pay adjusted to reflect either reduced working hours (part-time) or a reduced time period (for example, starting a role halfway through the year). This calculator is designed for common UK scenarios and gives a quick gross estimate you can use for planning, job comparisons, or offer discussions.
It calculates your salary in two stages:
- Hours adjustment: converts a full-time salary into your full-year equivalent based on your weekly hours.
- Period adjustment: if you enter dates, it estimates the gross salary for that specific date range.
Core formula
1) Convert full-time pay to your hours
Pro-rated annual salary = Full-time annual salary × (Your weekly hours ÷ Full-time weekly hours)
2) If calculating a specific period
Period salary = Pro-rated annual salary × Fraction of year worked − Unpaid leave deduction
The year fraction is calculated using actual days in each calendar year (including leap years), which gives a more accurate result for periods spanning different years.
Example (UK-style)
Suppose a role advertises £42,000 full-time at 37.5 hours/week. You work 30 hours/week:
- FTE ratio = 30 ÷ 37.5 = 0.80 (80%)
- Pro-rated annual salary = £42,000 × 0.80 = £33,600
- Approx monthly gross = £33,600 ÷ 12 = £2,800
If your employment period is only part of the year, your period total is then proportionally reduced.
When pro-rating is commonly used in the UK
- Part-time contracts
- Mid-year starts or leavers
- Term-time or seasonal roles
- Changes in contracted hours during the year
- Unpaid leave adjustments
Important notes before relying on the number
This calculator returns a gross estimate. Your payslip can differ due to payroll rules and deductions such as:
- PAYE tax code and taxable benefits
- National Insurance thresholds
- Pension contributions (including salary sacrifice)
- Student loan or postgraduate loan deductions
- Employer-specific pay-cycle and rounding methods
FAQ
Is this net pay?
No. It estimates gross pay before tax, National Insurance, pension, and other deductions.
Does leap year matter?
Yes. This calculator accounts for 366-day years when your selected period includes a leap year.
Should pro-rating be based on calendar days or working days?
Employers use different methods. This tool uses a calendar-based year fraction for period estimates, with a separate unpaid-leave deduction based on your estimated day rate.
Can I use this for offer comparisons?
Absolutely. It is useful for comparing part-time offers against full-time rates, especially when weekly hours differ between roles.
Disclaimer: This is an informational calculator, not payroll, tax, or legal advice.