Pro-rata holiday calculator
Work out pro-rata holiday if you join, leave or change your hours part-way through the leave year.
No data is stored on our servers. Everything stays in your browser. Privacy policy
"Pro-rata holiday" is not one calculation — it's three, and mixing them up is the most common way people either short-change themselves or over-promise an employee. Joining mid-year, leaving mid-year, and changing hours mid-year each use a different method, and the leaving calculation in particular follows a specific statutory formula that most online guides skip entirely.
Three different situations, three different sums
Every pro-rata query on this page reduces to one of three scenarios. Work out which one you're in before you touch a formula — the joining and leaving sums look similar on the surface but are not mirror images of each other.
| Your situation | What decides the sum | Jump to |
|---|---|---|
| You started (or start) mid-year | Days remaining in the leave year from your start date | Joining |
| You're resigning, retiring or being let go mid-year | A statutory formula — regulation 14 — comparing what you've accrued against what you've already taken | Leaving |
| Your contracted days or hours change mid-year | Two separate accrual periods, added together | Changing hours |
You're joining partway through the leave year
This is the straightforward case. Your employer works out how much of the leave year is left to run from your start date, and gives you that proportion of a full year's entitlement.
The method: count the calendar days from your start date to the last day of the leave year (inclusive), divide by the total number of days in the leave year, then multiply by your full annual entitlement — typically 5.6 weeks under Working Time Regulations 1998, regulation 13 and regulation 13A, capped at 28 days for a 5-day week.
This is a calendar-day method, not a working-day method — weekends and bank holidays inside the remaining period are not stripped out before you divide, because the 28-day (or 5.6-week) entitlement already bakes in an average working pattern. One wrinkle worth knowing: because you're partway through your first year of employment, the half-day rounding rule below applies to you as a firm requirement, not just an employer's choice.
You're leaving partway through the leave year
This is not the joining calculation run backwards. When you leave a job, your final holiday pay is governed by a specific statutory formula — Working Time Regulations 1998, regulation 14 — and almost no consumer-facing site sets it out in full.
Regulation 14 gives you:
(A × B) − C
- A — your leave entitlement under regulations 13 and 13A (the full 5.6 weeks, pro-rated for part-time hours)
- B — the proportion of your current leave year that had expired on your last day
- C — the leave you've already taken in that leave year
In plain terms: work out what you'd have accrued by your leaving date if you'd stayed the whole year (A × B), then subtract what you've already used (C). What's left is what your employer owes you in your final pay. It matters that C is taken away after the proportion is calculated — not before — because that's what makes this genuinely different from the joining sum, where there's no "already taken" figure to subtract at all.
There's also a 2024 addition worth knowing about if you're carrying leave from an earlier year: regulation 14(6), in force since 1 January 2024 under SI 2023/1426, extends the right to be paid in lieu to untaken leave that was carried forward from a previous leave year — not just leave accrued in the current one. Before this, only the current year's untaken leave was reliably covered by the statutory payment-in-lieu right.
You're changing your hours partway through
If your working pattern changes mid-year — say from full-time to part-time, or a change in your contracted days — the correct approach is to split the leave year into two (or more) periods at the point your hours changed, work out a separate pro-rata entitlement for each period at the pattern that applied during that period, and add the results together.
This matters because a single blended calculation across the whole year using either your old or new hours will misstate your entitlement in one direction or the other. Splitting the year respects what you actually worked, and it's the approach used throughout this calculator when you tell it about a hours change.
The rounding rule that works in your favour
Pro-rata sums rarely land on a whole number of days, so a rounding rule is needed — and the rule is asymmetric by design. Per ACAS guidance, employers can never round a part-day down. During your first year of employment, they must round any part-day up to the nearest half day. After your first year, they're free to round up if they choose to, but they don't have to — some employers track holiday down to the exact decimal day instead.
Three worked examples
Joining — Priya starts a five-day-a-week role on 1 September
Priya's leave year runs 1 April 2026 to 31 March 2027 (365 days), and her full entitlement for a five-day week is 28 days. She starts on 1 September 2026, leaving 212 days remaining in the leave year (1 September to 31 March inclusive).
212 ÷ 365 × 28 = 16.26 days → rounded up to 16.5 days (mandatory, as this falls in her first year of employment).
Leaving — Tom resigns after taking some leave already
Tom's leave year runs 1 January to 31 December 2026 (365 days). His full entitlement is 28 days (A). He resigns with his last working day on 15 June 2026 — 166 days into the leave year (B = 166 ÷ 365). He has already taken 10 days' leave (C) since 1 January.
A × B = 28 × (166 ÷ 365) = 12.73 days accrued by his leaving date.
(A × B) − C = 12.73 − 10 = 2.73 days owed in his final pay (an
employer applying the optional half-day round-up would pay 3.0 days).
Changing hours — Sam drops from five days to three days a week
Sam's leave year runs 1 January to 31 December 2026. He works a five-day week (28 days' full entitlement) from 1 January to 30 June — 181 days — then drops to a three-day week (16.8 days' full entitlement, being 5.6 weeks × 3) from 1 July to 31 December — 184 days.
Period 1: 181 ÷ 365 × 28 = 13.88 days.
Period 2: 184 ÷ 365 × 16.8 = 8.47 days.
Total: 13.88 + 8.47 = 22.35 days → rounded up to 22.5 days.
What your employer cannot do
- Round a part-day of holiday down, at any point in your employment (ACAS).
- Withhold payment in lieu of statutory leave you've accrued but not taken when you leave — regulation 14 requires it to be paid.
- Deduct pay for holiday you've over-taken unless a payback clause was agreed in your contract or in writing beforehand (ACAS).
- Ignore untaken leave carried forward from an earlier leave year when calculating your final pay — regulation 14(6), in force since 1 January 2024, brings carried-forward leave into the payment-in-lieu calculation too.
Frequently asked questions
How is pro-rata holiday calculated if I'm joining mid-year?
Count the calendar days from your start date to the end of the leave year, divide by the total days in the leave year, then multiply by your full annual entitlement. For example, starting a 28-day-a-year role on 1 September with 212 days left in a 365-day leave year: 212 ÷ 365 × 28 = 16.26 days, rounded up to 16.5 days.
Is holiday calculated differently when leaving a job?
Yes. Leaving uses Working Time Regulations 1998, regulation 14: (A × B) − C, where A is your full entitlement, B is the proportion of the leave year that had expired on your last day, and C is leave already taken. It is not the same sum as joining, because it subtracts leave you've already used.
What if I've taken more holiday than I've accrued when I leave?
Under ACAS guidance, an employer can only deduct the excess from your final pay if that was agreed in your contract or in writing beforehand — a payback clause. Without prior written agreement, they generally cannot claw it back through wage deductions.
How do I calculate pro-rata holiday when my hours change mid-year?
Split the leave year into separate periods at the point your hours changed, calculate a pro-rata entitlement for each period using the pattern that applied during it, then add the results together.
Does UK law require rounding up part days of holiday?
During your first year of employment, ACAS guidance says employers must round part-days up to the nearest half day. After the first year, rounding up becomes optional, though employers can never round down.