Pro-rata salary calculator, 2026/27

How this is calculated

The pro-rata salary is simply the full-time equivalent salary multiplied by the ratio of actual contracted hours to standard full-time hours, so someone working 22.5 hours out of a standard 37.5-hour week receives 60% of the full-time salary. Income tax and employee National Insurance are then calculated on this reduced figure using the same 2026/27 bands and thresholds that apply to any salary, £12,570 personal allowance, 20%/40%/45% tax bands and 8%/2% NI rates.

Because thresholds like the £12,570 personal allowance and NI primary threshold are fixed amounts rather than being pro-rated, part-time workers on lower pro-rata salaries often pay a much smaller proportion of their income in tax and NI than full-time colleagues on the equivalent full salary.

Pro-rata beyond salary

Holiday entitlement, sick pay qualification, and some contractual benefits should also be pro-rated using the same hours ratio, based on the statutory 5.6 weeks annual leave entitlement, so a part-time worker on 60% of full-time hours is entitled to 60% of the full-time holiday allowance, not the full 5.6 weeks. Bonuses and other variable pay are commonly, though not automatically, pro-rated in the same way, and this should be set out clearly in the employment contract.

Pension contributions under auto-enrolment are based on actual qualifying earnings rather than the pro-rata calculation itself, so contributions naturally scale with the reduced salary without needing a separate adjustment.

Practical points for employers

When advertising or agreeing part-time roles, always state both the full-time equivalent salary and the actual pro-rata salary, so candidates and existing staff moving to reduced hours understand exactly what they will be paid. Keep hours records accurate, since even small discrepancies compound noticeably once translated into an annual salary figure.

Is pro-rata salary calculated on hours or days?

Either can be used, but hours is more common and more accurate where daily hours vary. Whichever method is used should be applied consistently to salary, holiday and any other pro-rated benefits.

Do part-time workers pay less tax proportionally?

Often yes, because the £12,570 personal allowance and NI thresholds are fixed amounts, not scaled down for part-time hours, so a smaller pro-rata salary can fall largely or entirely within the tax-free allowance.

Should holiday entitlement be pro-rated the same way as salary?

Yes, using the same hours or days ratio applied to the statutory 5.6 weeks minimum annual leave entitlement, so a 60% full-time equivalent role receives 60% of the full-time holiday allowance.

Does pro-rata pay affect pension auto-enrolment?

No, auto-enrolment eligibility and contribution amounts are based on actual qualifying earnings paid, which already reflects the pro-rata salary, so no separate pro-rata adjustment to pension figures is needed.