Part month salary calculator
Start or leave a job part way through a month and your payslip is a fraction of the usual one. Which fraction depends on whether your employer splits the month by calendar days or working days, and the two do not agree. This works out both, and what each leaves after tax.
Calculator
Calculator
Starting on 15 April, you are paid for 16 of 30 calendar days
£1,253.30
after tax, against £2,093.30 in a full month. Gross for the period is £1,333.33.
Both bases, side by side
The same start date pays differently depending on which split your employer uses.
| Basis | Days paid | Gross | After tax |
|---|---|---|---|
| Calendar days | 16 of 30 | £1,333.33 | £1,253.30 |
| Working days | 12 of 22 | £1,363.64 | £1,275.12 |
2026/27 rates. Tax on a part month is worked out on the pay you actually receive in that period, so the deduction rate is usually lower than a full month's.
How is a part month calculated?
A part month is your monthly salary scaled to the days you are employed. On the calendar basis, that is the days from your start date to the end of the month divided by the days in that month. Starting on 15 April means 16 of 30 days, so £30,000 a year pays £1,333.33 gross rather than the usual £2,500.00. On the working-day basis, only the days you would have worked count, which changes the answer whenever a month’s weekends fall unevenly.
Why the tax on a part month is proportionally lower
PAYE is worked out on the pay you actually receive in the period, against a twelfth of your personal allowance. A part month earns less but still gets a full month’s slice of allowance, so a larger share of it is sheltered. On the example above the part month keeps £1,253.30 of £1,333.33, a higher proportion than the £2,093.30 kept from a full £2,500.00.
What this calculator assumes
- The standard 1257L tax code, and that this is your only job.
- An evenly paid salary with no bonus or overtime in the part month. Add pension and student loan on the main calculator.
- Working days are counted as a typical five-day week for that month, so a bank holiday you are paid for is included. Your employer’s own count may differ by a day.
2026/27 HMRC rates, checked 28 August 2026 by Hadi. Method and sources on the about page.
How to use the part month salary calculator
- 1
Enter your annual salary and say whether you are starting or leaving.
- 2
Pick the month and the day, since the number of days in that month changes the fraction.
- 3
Choose calendar days or working days, whichever your contract specifies.
- 4
Read the pay for the period and compare both bases in the table, because they rarely agree.
When should you use the part month salary calculator?
Use it for a first or last payslip, when you are paid for only part of a month and want to know what will actually arrive.
Starting a job mid-month
Your first payslip covers only the days from your start date, not the whole month.
Leaving a job mid-month
Your last payslip covers the days up to your leaving date, plus any untaken holiday.
Your first payslip looks wrong
A new starter without a P45 is often taxed on an emergency code, which takes too much.
Checking your employer's sums
Calendar days and working days give different answers on the same start date.
Where to go next
- Tax code checkerTo check whether an emergency code took too much from that first payslip.Open
- Pro rata salary calculatorTo scale a salary to reduced hours rather than to part of a month.Open
- Payslip checkerTo recalculate every line of the payslip that arrives.Open
All 43 tools share one tested engine, so a figure from the part month salary calculator agrees with every other page here. See the full calculator index or the pay and tax guides.