How to Calculate Part-Time Holiday Entitlement in the UK

If you employ part-time staff, you are legally required to give them a fair share of annual leave. But working out exactly how many days or hours that amounts to can be confusing, especially when people work irregular patterns or change their hours mid-year.

This guide walks you through how to calculate part-time holiday entitlement in the UK step by step, with worked examples you can apply straight away. For a broader overview of statutory leave rules, see our UK holiday entitlement guide.

What the law says

Under the Working Time Regulations 1998, almost all workers in the UK are entitled to 5.6 weeks of paid annual leave per year. For a full-time employee working five days a week, that works out to 28 days (5 x 5.6). This is the statutory minimum; employers can offer more but never less.

Part-time workers have exactly the same right to 5.6 weeks of leave. Because they work fewer days each week, their entitlement is calculated on a pro-rata basis. The Part-Time Workers (Prevention of Less Favourable Treatment) Regulations 2000 make it unlawful to treat part-time staff less favourably than full-time colleagues, and that includes holiday allowance.

The pro-rata formula

The standard formula for part-time holiday entitlement is straightforward:

Days worked per week x 5.6 = annual holiday entitlement (in days)

This gives you the statutory minimum in days. If your organisation offers more than 5.6 weeks to full-time staff, replace 5.6 with the equivalent multiplier. For example, if full-time employees get 33 days, the multiplier is 33 / 5 = 6.6.

Worked examples

Example 1: Three days per week

A member of staff works Monday, Wednesday, and Friday every week.

• 3 days x 5.6 = 16.8 days of annual leave per year

Each "day" of leave covers one of their normal working days, so 16.8 days means they can take roughly sixteen and a half working days off across the year.

Example 2: Two and a half days per week

A member of staff works Monday, Tuesday, and Wednesday morning (counting the half-day as 0.5).

• 2.5 days x 5.6 = 14 days of annual leave per year

Example 3: Four days per week

A member of staff works Tuesday to Friday.

• 4 days x 5.6 = 22.4 days of annual leave per year

Notice the maximum statutory entitlement is capped at 28 days, so even if someone technically works more than five days a week, they cannot receive more than 28 days under the statutory minimum.

Calculating entitlement in hours (for irregular hours workers)

Not every part-time worker follows a neat pattern of whole days. Some work different hours on different days, or their shifts vary from week to week. In these cases, it is usually easier and fairer to calculate entitlement in hours rather than days.

The formula is:

Hours worked per week x 5.6 = annual holiday entitlement (in hours)

Example: 18 hours per week

• 18 hours x 5.6 = 100.8 hours of annual leave per year

When a member of staff books a day off, you deduct the number of hours they were scheduled to work that day. So if they were due to work six hours on a Thursday, booking that Thursday off uses six hours of their allowance rather than a flat "one day."

Irregular or annualised hours

From 1 January 2024, the Working Time Regulations introduced a specific method for calculating holiday entitlement for irregular hours and part-year workers. Under this method, entitlement accrues at 12.07% of hours worked in each pay period. This is particularly relevant for zero-hours contract workers, term-time-only staff, and anyone whose hours genuinely vary from week to week.

For workers on set weekly hours, the 5.6-week formula above remains the simplest and most accurate approach.

Bank holidays and part-time staff

This is one of the most common areas of confusion. There is no standalone legal right to take bank holidays off in the UK. The 5.6 weeks of statutory leave can include bank holidays or be separate from them; it depends on the employment contract.

The important principle is fairness. If full-time staff receive bank holidays on top of their 28 days, part-time staff must receive an equivalent pro-rata benefit. Here is a practical way to handle it:

1. Calculate the full-time total: 28 statutory days + 8 bank holidays = 36 days.
2. Pro-rata for the part-time worker: (days per week / 5) x 36.
3. Deduct a day from their allowance whenever a bank holiday falls on one of their normal working days.

Example

A worker does three days a week (Monday, Tuesday, Wednesday). The company gives full-time staff 28 days plus 8 bank holidays (36 total).

• (3 / 5) x 36 = 21.6 days total leave allowance
• If five of the eight bank holidays fall on a Monday (one of their working days), those five days are deducted automatically.
• They have 21.6 - 5 = 16.6 days remaining to book as they choose.

A worker who does Thursday and Friday would only lose bank holidays that land on those days (far fewer), so they end up with more discretionary leave. Over the year the total entitlement in weeks remains equal, which is what the law requires.

Rounding fractional days

The pro-rata formula often produces decimals such as 16.8 or 22.4 days. There is no legal requirement to round up, but employers are not allowed to round down. You have a few options:

• Round up to the nearest whole or half day. This is the simplest approach and keeps you on the right side of the law. For example, 16.8 days becomes 17 days.
• Keep the decimal and track precisely. Many leave management tools let you track entitlement to one or two decimal places, so a worker genuinely gets 16.8 days.
• Work in hours instead. If you convert everything to hours, fractional days disappear entirely because you deduct exact hours when leave is booked.

Whichever method you choose, apply it consistently across all staff to avoid claims of unfair treatment.

When part-time patterns change mid-year

It is common for employees to change their working pattern during the leave year, for instance dropping from four days to three after returning from parental leave. When this happens, you need to split the year and calculate entitlement for each period separately.

Step-by-step method

1. Work out how many complete weeks fall in each period.
2. Calculate the weekly leave accrual rate for each pattern (days per week / 5 x 28 / 52).
3. Multiply each accrual rate by the number of weeks in that period.
4. Add the two figures together for the total annual entitlement.

Example

An employee works four days a week for the first 30 weeks of the leave year, then changes to three days a week for the remaining 22 weeks.

• Period 1: 4 days x 5.6 = 22.4 days full-year equivalent. For 30 weeks: 22.4 x (30 / 52) = 12.92 days.
• Period 2: 3 days x 5.6 = 16.8 days full-year equivalent. For 22 weeks: 16.8 x (22 / 52) = 7.11 days.
• Total entitlement for the year: 12.92 + 7.11 = 20.03 days.

Remember to check how much leave has already been taken under the old pattern before communicating the new balance to the employee.

Starters and leavers part-way through the year

When a part-time worker joins or leaves part-way through the leave year, you need to pro-rata their entitlement based on the proportion of the year they have worked (or will work).

The formula is:

Full-year entitlement x (remaining calendar days in the year / 365)

Example

A three-day-per-week worker joins on 1 July with a leave year running January to December. There are 184 days remaining in the year.

• Full-year entitlement: 3 x 5.6 = 16.8 days.
• Pro-rata for the period: 16.8 x (184 / 365) = 8.47 days.

For a leaver, follow the same approach but for the portion of the year already worked. If they have taken more leave than they have accrued, you may be able to reclaim the difference from their final pay, provided this is set out in their contract.

Common mistakes to avoid

• Rounding down. Always round up or keep the exact decimal. Rounding down means giving less than the statutory minimum, which is unlawful.
• Forgetting the 28-day cap. Statutory entitlement is capped at 28 days regardless of how many days someone works. A six-day-per-week worker still only gets 28 days by law (though you can contractually offer more).
• Treating bank holidays inconsistently. If full-time staff get bank holidays on top of their allowance, part-time staff must receive the pro-rata equivalent.
• Using the wrong leave unit. If you track leave in days but a part-time worker does different hours each day, you could over- or under-deduct. Switching to hours solves this.
• Not adjusting for mid-year changes. A pattern change means you need to recalculate, not simply apply the new pattern to the full year.

Quick reference table