Irish Calculators
Work & pay

Pro Rata Gross Salary for Part-Time Hours

Calculate an annual-equivalent gross salary from the ratio of agreed hours to full-time hours. The optional month fraction is a scenario, not a legal rule for a partial-month payslip.

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Your numbers

€
Your figures stay on this device.

How the calculation works

Pro-rata salary scales a full-time annual salary by the ratio of agreed hours to full-time hours. It then shows a monthly equivalent and an optional fraction of that annual amount, without selecting a payroll rule for a partial calendar month.

FTE fraction = agreed hours ÷ full-time hours. Annual pro-rata salary = full-time annual salary × fraction. Period equivalent = annual pro-rata salary × months/12.

  1. Find the hours fraction

    Divide agreed weekly hours by full-time weekly hours. A half-time schedule produces a fraction of 0.5; the calculation itself does not cap the ratio at one.

  2. Scale annual salary

    Multiply full-time annual salary by that fraction. This produces a gross annual equivalent for the stated hours, with no automatic overtime premium.

  3. Express the selected period

    Divide annual pro-rata salary by twelve for the monthly equivalent. Multiply it by months divided by twelve for the chosen period equivalent.

Worked example: Half time

Sample inputs demonstrate the method. They are not a forecast or product offer.

The first example uses €40,000 full-time annual pay, 40 full-time weekly hours and 20 agreed hours. The fraction is 20/40, or 0.5, giving €20,000 annual pro-rata salary. With twelve months selected, the period equivalent is the same amount.

Full-time annual salary (€)
40000
Full-time weekly hours
40
Agreed weekly hours
20
Months of annual-equivalent pay
12

Expected result

Pro-rata annual salary
€20,000.00
Worked example: Three-quarter time

Sample inputs demonstrate the method. They are not a forecast or product offer.

Full-time annual salary (€)
60000
Full-time weekly hours
40
Agreed weekly hours
30
Months of annual-equivalent pay
6

Expected result

Pro-rata annual salary
€45,000.00

Understanding your result

The annual result is based on relative hours, not the number of calendar days in a particular month. Changing the month fraction affects the selected-period result without changing annual salary.

A partial-month payslip can follow calendar-day, working-day or other agreed conventions. This tool only applies the supplied annual fraction and does not decide which convention is required.

Questions you might have

What does this pro rata salary calculator include?

Calculate an annual part-time salary and a period-equivalent amount from a full-time salary and agreed working hours.

Which assumptions should I check?

Calendar-day and working-day payroll proration conventions differ. The month fraction here is a scenario and is not a determination of a partial-month payslip.

Choosing the right inputs

Full-time annual salary
Use the full-time annual gross salary for the relevant role or arrangement, rather than a part-time amount that has already been reduced.
Full-time weekly hours
Enter the positive weekly hours represented by that full-time salary. Agreed weekly hours must use the same definition of paid or contracted time.
Months of annual-equivalent pay
Enter zero to twelve months of annual-equivalent pay, including a fractional month if that is the scenario required. This fraction is not an inferred calendar-day payroll divisor.

Common mistakes to avoid

  • Do not pro-rate an already reduced salary again unless a second independent reduction is intended.
  • Hours above the full-time basis increase the arithmetic result but do not establish entitlement to pay those hours at an ordinary rate.

Assumptions to check

  • Calendar-day and working-day payroll proration conventions differ. The month fraction here is a scenario and is not a determination of a partial-month payslip.

Sources and method

Read our calculation and testing approach.