UK Pro-Rata Salary Calculator — Methodology

Last verified 5 May 2026 against ACAS working time and pay guidance. Calculator at /uk/salary/pro-rata-salary-calculator/.

What this calculator does

Converts a full-time-equivalent (FTE) salary into part-time, hourly, daily, weekly, or monthly equivalents based on contracted hours and working pattern.

The formula

prorataAnnual = fteAnnual × (partTimeHours / fteHours)
weekly  = prorataAnnual / 52
monthly = prorataAnnual / 12
daily   = prorataAnnual / workingDaysPerYear
hourly  = prorataAnnual / (partTimeHours × 52)

Default FTE = 37.5 hrs/week, 260 working days/year.

Authoritative sources

• ACAS — pay and wages
• Holiday entitlement (gov.uk)
• National Minimum Wage rates

Assumptions and limitations

• Pure proportional conversion — no allowance for shift premia, overtime, or unsocial hours uplifts.
• Holiday accrual (5.6 weeks statutory minimum) is not converted into pay; this is a salary calculator, not a holiday calculator.
• Bank holidays are assumed to be included in the 5.6-week entitlement unless the contract says otherwise.
• National Minimum Wage compliance must be checked separately for low-hours conversions.

Source data

This calculator is rate-free — it does not depend on a tax-year rate table. The methodology and assumptions above are the source of truth.

Verification log

• 5 May 2026: Pro-rata logic is rate-free; reviewed against ACAS guidance during audit cycle 5