Why this exists
GOV.UK publishes a holiday entitlement calculator, and for the simplest case — someone working the same fixed days every week, all year — it’s fine. Outside that case, it gets vague fast. Term-time staff, zero-hours contracts, seasonal workers, and anyone who started or left partway through the year are told, in effect, to work it out themselves. This tool does that working-out, using the actual statutory formulas rather than a rough approximation.
The three formulas, briefly
- Regular week: 5.6 statutory weeks × your contracted days per week, capped at 28 days for a full-time equivalent.
- Starting or leaving mid-year: your full annual entitlement, pro-rated by the proportion of the leave year you’re actually employed.
- Term-time or irregular hours: hours worked across the year × 12.07% — the statutory rate since 1 January 2024 for anyone with genuine unpaid weeks or wholly variable hours.
The third one is the case most calculators skip entirely, and it’s also the one where getting it wrong is most common — before the 2024 regulations, the case law (Harpur Trust v Brazel, 2022) had pushed employers toward a 52-week averaging method for these workers, which the 2024 rules deliberately replaced with 12.07% specifically to make this easier to calculate correctly.
Worked example: a term-time teaching assistant
Someone working 32.5 hours a week, term-time only, across 39 weeks a year: 32.5 × 39 = 1,267.5 hours worked. 1,267.5 × 12.07% ≈ 153 hours of statutory leave — worth roughly 23.5 days at a 6.5-hour working day. Run the same numbers through the calculator above under “Term-time or irregular hours” to see it broken down.
A note on accuracy
This calculates the statutory minimum under the Working Time Regulations 1998, as amended by the Employment Rights (Amendment, Revocation and Transitional Provision) Regulations 2023. It doesn’t account for enhanced contractual entitlement, maternity/paternity leave, long-term sickness, or TUPE transfers — all of which can change the number. Treat the result as a floor, not a final answer for a dispute.