Part-month salary calculator
Estimate gross salary for one month when you start, leave or have an unpaid period. Choose calendar dates or the paid-day counts agreed with your employer.
Choose the method your employer uses
A part month can arise when you start a job, leave it or have an unpaid period. This calculator estimates gross salary for one selected month. It divides annual salary by twelve, then multiplies that monthly amount by the share of the month you enter. Your contract or payroll method controls the real payslip. There is no single salary divisor that applies to every job.
The calendar-day method counts every date from your start date to your end date, including both dates. Weekends and other days you do not work still count. The denominator is the number of calendar days in the selected month. Choose dates in that month; a period crossing into another month needs a separate calculation for each month.
The agreed paid-day method uses the paid days and total days you supply. Use the day counts your employer agrees for that month, including paid holiday where the employer counts it. The calculator does not assume you work Monday to Friday. Fractional days can have up to two decimal places, and paid days can be zero. The paid count must not exceed the total.
A worked example
For an annual salary of £36,000, the monthly amount is £3,000. In September 2026, the dates 16 September 2026 to 30 September 2026 give 15 days out of 30. Multiplying the monthly amount by that fraction gives £1,500 gross pay. With the agreed paid-day method, 11 paid days out of 22 gives the same estimate.
The calculation keeps the unrounded monthly salary until the last step. It rounds the final estimate once to pennies, with an exact half penny rounded up. Rounding the monthly salary first can change the answer.
What to check alongside the estimate
Changing weekly hours is a different calculation. The pro rata salary calculator compares contracted hours, and the hourly pay converter converts an hourly rate into weekly or annual pay.
When leaving a job, check the notice period calculator and your contract. Notice pay and holiday adjustments can affect final pay. The holiday entitlement calculator can help you examine a separate holiday calculation. This part-month result does not establish notice entitlement or final pay.
Tax, National Insurance and other deductions are outside this calculation. The take-home pay calculator provides a full-year estimate; it does not turn this month's gross amount into a guaranteed net payment. If a redundancy payment is also involved, redundancy pay after tax covers that separate payment.
Questions
Does the calendar method include weekends?
Yes. It counts all dates in the period, including the start and end dates, whether or not you normally work on them.
Which method should I choose?
Use the method in your contract or ask payroll how they apportion salary. The two methods here illustrate different ways to divide a monthly salary, and can produce different amounts.
Is this my final payslip?
No. Final pay can include holiday adjustments, notice pay and other amounts. Check the pay period and ask payroll to explain the calculation on your payslip.
Source and assumptions
This is an illustration of gross salary apportionment, for information only. Acas guidance on final pay explains why final pay can differ and why the payslip calculation matters. Acas does not prescribe the two formulas used here.
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