To work out a part-time salary you need three numbers: the full-time salary, the full-time hours it assumes, and your hours. Divide, multiply, done, £33,000 at 20 of 37.5 hours is £17,600 gross. The fourth number, the one the bank account sees, is £16,191.60: the gross after 2026/27 income tax and National Insurance, which this page and the linked calculator both compute from the published rates.
The three-line method
Line one: hourly value = full-time salary ÷ (full-time weekly hours × 52). For £33,000 on 37.5 hours that is £16.92. Line two: your gross = hourly value × your weekly hours × 52. At 20 hours: £17,600. Line three: the tax. The first two lines are proportion; the third is not, because the allowance and thresholds are fixed sums that favour the smaller gross. Skipping line three is how part-time offers get misjudged.
Sanity checks that catch most errors
Your gross ÷ the FTE must equal your hours fraction exactly. Your hourly rate must equal the full-timer's: if it comes out lower, the offer breaches the part-time regulations' equal-treatment floor. And the payslip's period gross must be the annual figure ÷ 12 (or ÷ 52 for weekly pay): £17,600 a year is £1,466.67 a month. Any payslip that disagrees with all three checks at once is using different hours than the ones you agreed.
From gross to pocket at typical part-time levels
£12,000 a year sits under both thresholds, so it pays no income tax and no National Insurance at all: take-home the full £12,000.00. £17,600: take-home £16,191.60 at 8% deducted. £22,000: take-home £19,359.60 at 12%. The deduction share climbs slowly from zero as pay rises above the £12,570 allowance: a part-time salary is the cheapest tax band you will ever be in.
Questions people ask about work out part time salary
What if the advert gives an hourly rate, not a salary?
Then you are one line in: rate × your weekly hours × 52 is your gross, and the tax step is identical.
How do term-time-only contracts change the method?
The fraction becomes paid weeks ÷ 52 as well as hours ÷ full-time hours: multiply both fractions before applying the salary.
Why is my monthly pay the same in short and long months?
Salaried pay is the annual figure ÷ 12 regardless of working days; only hourly-paid work varies with the calendar.