Pro Rata Holiday Calculator UK: Part-Time Annual Leave

If you work part-time, figuring out exactly how much paid holiday you’re entitled to can feel like guesswork. Your full-time colleagues get 28 days, but what does that mean for someone working three days a week — or irregular shifts? A pro rata holiday calculator UK workers can rely on starts with one simple principle: part-time staff must get the same holiday rights as full-time staff, scaled down in proportion to the hours they work.

In this guide, we’ll walk through the statutory rules, the exact formula employers should use, and worked examples for the most common part-time patterns. By the end, you’ll be able to check your own entitlement in about two minutes — and spot it quickly if your employer has short-changed you.

How statutory holiday works in the UK

Under the Working Time Regulations 1998, almost every worker in the UK is entitled to a minimum of 5.6 weeks of paid annual leave each leave year. For someone working a standard five-day week, that works out at 28 days — and employers are allowed to count the usual eight bank holidays as part of those 28 days.

The key point: part-timers get the same rights, scaled. The law says part-time workers must not be treated less favourably than comparable full-time workers, so your holiday is calculated pro rata — in direct proportion to your pattern.

So if a full-time employee working five days a week gets 28 days, someone working two and a half days should get exactly half of that: 14 days. Simple in theory, but the details matter, especially when shifts are irregular or you started part-way through the year.

The pro rata holiday formula

The standard formula most UK employers use is refreshingly straightforward:

Your annual leave = 28 days × (your days worked per week ÷ 5)

Or, if you think in hours rather than days:

Your annual leave in hours = 28 days × full-time daily hours × (your weekly hours ÷ full-time weekly hours)

Let’s put the first version to work. Imagine Priya works three days a week, Monday to Wednesday, in a retail head-office role. Her full-time colleagues work five days and get 28 days of leave including bank holidays.

Priya’s entitlement = 28 × (3 ÷ 5) = 16.8 days.

That 0.8 of a day is awkward in practice, so most employers round up to the nearest half or full day — 17 days here. Rounding down risks dropping you below the statutory minimum, which is unlawful, so ask for the rounding policy in writing.

A quick note on bank holidays

Those 28 days include bank holidays where your employer counts them inside the entitlement — which most do. This matters a lot for part-timers, as we’ll see in the bank holiday section below, because if you don’t normally work Mondays (when most bank holidays fall), you could end up effectively worse off unless your employer adjusts. The fair approach, endorsed by Acas, is to give part-time staff a pro rata bank holiday allowance on top of, or calculated within, their leave.

Pro rata holiday table: days worked to leave entitlement

The table below shows statutory minimum entitlement for common part-time patterns, based on the 28-day full-time figure. Use it as a fast check against what your contract or payslip says.

Remember: this is the legal minimum. Many employers offer more generous contractual holiday — 30, 33 or even 35 days for full-time staff — and the same pro rata principle applies to the enhanced amount. Always check your contract first; the statute is just the floor.

Worked example: putting a £ value on your holiday

Holiday entitlement isn’t just about days off — each day has a cash value, which matters if you leave a job with untaken leave or want to understand what your leave is really worth. Here’s how to value it.

Take Daniel, who works four days a week (30 hours) on a pro rata salary of £24,000 a year. His full-time colleagues work 37.5 hours for £30,000.

Step 1 — Daniel’s leave entitlement: 28 × (4 ÷ 5) = 22.4 days.

Step 2 — Daniel’s daily rate: A full-time year has roughly 260 working days (52 weeks × 5 days). Daniel works 4 days a week, so his working year is about 208 days. His daily rate = £24,000 ÷ 208 = £115.38 per day.

Step 3 — Value of his annual leave: 22.4 days × £115.38 = £2,584.62 of paid time off each year.

That figure is useful context: if Daniel left the company with, say, 6 days of untaken holiday, he’d be owed roughly 6 × £115.38 = £692.31 in his final pay (before tax and National Insurance, and subject to the exact accrual rules we’ll cover in our guide to unused holiday).

Irregular hours and part-year workers: the 12.07% rule

Not everyone works neat, fixed days. If your hours vary week to week — zero-hours contracts, term-time casual work, seasonal shifts — the simple days-based formula doesn’t fit. For these workers, the rules changed for leave years beginning on or after 1 April 2024.

Under the current regulations, irregular-hours workers and part-year workers now accrue holiday as they go: for each pay period, you build up leave equal to 12.07% of the hours you actually worked.

Why 12.07%? It’s 5.6 weeks ÷ (52 weeks − 5.6 weeks) — the statutory entitlement expressed as a proportion of time worked. In practice:

Holiday hours accrued = hours worked in the pay period × 0.1207

Example: Sofia works variable hospitality shifts. In June she works 96 hours. Her accrued holiday for June = 96 × 0.1207 = 11.59 hours — roughly a day and a half of leave banked for that month alone.

Employers may also use rolled-up holiday pay for these workers: instead of paying you when you take leave, they add an extra 12.07% to your hourly pay each period, labelled clearly on the payslip as holiday pay. This is now explicitly lawful for irregular-hours and part-year workers, though it remains unlawful for regular fixed-hours staff.

If you were employed before April 2024 on variable hours, your employer should have moved you onto one of these methods — it’s worth checking your payslips and contract to see which.

Starting or leaving mid-year

Holiday entitlement is usually expressed as a full-year figure, but if you join in July or leave in October, you’re only entitled to the slice of the year you actually worked. The standard approach is monthly accrual:

Accrued leave = annual entitlement × (complete months worked ÷ 12)

Take Amara, who works three days a week (16.8 days annual entitlement) and leaves her job at the end of September after 9 complete months. Her accrued entitlement = 16.8 × (9 ÷ 12) = 12.6 days. If she’s already taken 10 days, her employer owes her 2.6 days’ pay in her final settlement. If she’d taken 14 days, she might owe the employer for the 1.4 days over-taken — though many employers write this off, and contracts vary, so check yours.

One trap to avoid: some employers try to apply a “probationary” delay to holiday. There’s no legal basis for withholding your statutory minimum — from day one of employment, you accrue it, even during probation.

What if your employer gets it wrong?

Underpayment of holiday is one of the most common payroll errors for part-time staff, and it’s often accidental — a spreadsheet that wasn’t updated when someone dropped a day, or bank holidays handled badly. Here’s a practical checklist:

1. Get your contract figure. Find your contractual annual leave (in days or hours) and confirm whether bank holidays are included or additional.
2. Run the pro rata maths. Use the formula or table above. For variable hours, check whether 12.07% accrual is being applied.
3. Check bank holiday treatment. If you don’t work Mondays and your employer hasn’t adjusted, you may be missing out — raise it.
4. Put it in writing. Email your manager or HR with your calculation and ask for a breakdown of theirs. Keep it factual and polite; most discrepancies are fixed at this stage.
5. Escalate if needed. If your employer won’t correct it, you can raise a formal grievance, contact Acas for free advice, and ultimately bring a claim to an employment tribunal — but be aware of strict time limits (usually three months less one day from the underpayment).

Keep your own simple log too: days worked, leave requested and taken, and payslip holiday-pay lines. If a dispute arises, contemporaneous records are gold.

Frequently asked questions

Do part-time workers get bank holidays off paid?

Not automatically as extra days. If your employer includes bank holidays within the 28-day minimum, a part-timer gets a pro rata share of bank holiday entitlement — for example, someone working three days a week gets 4.8 days of bank holiday allowance (8 × 3 ÷ 5). How it’s administered varies: some employers add it to your leave pot, others give time off in lieu when a bank holiday falls on your non-working day. The outcome should be that you’re not disadvantaged compared with full-time colleagues.

Can my employer round my 16.8 days down to 16?

They shouldn’t. Rounding down risks dropping you below the statutory minimum, which is unlawful. The safe and standard practice is to round up — to 17 days in this case — or to track the fraction in hours. If your employer rounds down, challenge it: the law requires the full 5.6-week equivalent.

Does overtime count towards my holiday entitlement?

It depends on the overtime. Guaranteed contractual overtime usually counts towards your “normal” working pattern for holiday calculations. Voluntary overtime is trickier, but case law has established that regular voluntary overtime should be reflected in holiday pay (the rate you’re paid while on leave). For the amount of leave, though, the days-based pro rata formula normally uses your contracted days. If you regularly work extra days, talk to HR about whether your pattern has effectively changed.

I work term-time only — does the 12.07% rule apply to me?

Quite possibly. Term-time-only staff are typically classed as part-year workers, so for leave years starting on or after 1 April 2024, many employers now accrue their holiday at 12.07% of hours worked rather than using the old flat percentage-of-year method. In practice, schools and councils usually bake an additional holiday allowance into the term-time salary calculation instead — so check how your employer expresses it before assuming anything is missing.

How do I calculate pro rata holiday entitlement?

Multiply the days you work each week by 5.6 (or your weekly hours by 5.6), capped at 28 days. If your contract gives full-time staff more than 28 days, take that full-time figure and multiply it by your days divided by full-time days.

How many days of holiday is 3 days a week?

16.8 days at the statutory minimum (3 × 5.6), which is 126 hours if your days are 7.5 hours long. If your employer counts bank holidays within it, they come out of that figure.

Should I calculate pro rata holiday in days or hours?

Either works. Hours are safer when your shifts differ in length, because a day off then costs a different number of hours each time. The calculator above shows both.