So, you’ve finally got the boss to agree to you going part-time to fit around school pick-up and those Tuesday morning ukulele lessons. Or you’ve upgraded to a sweet full-time position, and you’re drooling over the extra cash. But wait, what about your holidays? When you change your hours, will your holiday allocation keep pace? Will it shrink to fit part-time? Expand for full-time? How much by? And what about the bank holidays? WHAT ABOUT THE BANK HOLIDAYS?
This article is for anyone who’s stared in mystification at holiday entitlement calculations after a change in hours. Whether you’re in HR and need a refresh or you’re an employee moving between full and part-time roles, we’ll run through the process of converting holiday entitlement.
Converting annual leave from days to hours (and vice versa) and making pro-rata adjustments isn’t just about simple arithmetic. It’s an essential part of looking after employees. It keeps things fair and legally compliant and avoids headaches for everyone.
Table of Contents:
- Why does leave need to be converted?
- The (not-so-secret) formula for leave conversion
- What about irregular hours?
- Common conversion conundrums (and how to solve them)
- Why getting It right matters
- Oi, leave over!
Why does leave need to be converted?
Leave needs to be converted when you change between full-time and part-time so that all workers are treated the same, no matter what their hours are. It’s a UK legal requirement designed to keep working conditions fair for everyone.
Holiday entitlement in the UK is pro-rata. That means the amount of holiday you get is worked out proportionally according to how much you work.
The calculations can seem like a bit of a mind-bend, but don’t worry, we’ve broken it down step by step.
- All workers in the UK are entitled to 5.6 weeks paid holiday per year.
- How many actual days that becomes depends on how much you work in a week.
There’s some simple maths for working out how this applies to you. You multiply your number of working days by 5.6. Here are a couple of examples:
- If you work full time 5 days a week, you are entitled to 28 days holiday per year. That’s:
⦿ 5 days x 5.6 weeks = 28 days
2. If you work part-time 3 days a week, you get 16.8 days of holiday per year.
⦿ 3 days x 5.6 weeks = 16.8 days
Changing from part-time to full-time work (or the other way round) changes the number of holiday days you get. There’s a bit more maths to do to work out the change. (Only a bit, honestly.)
The (not-so-secret) formula for leave conversion
Don’t worry; ‘formula’ makes it sound worse than it is. Here’s a step-by-step process for how to work out holiday entitlement from hours worked. We’ll use the abbreviations FT (full-time) and PT (part-time) here.
- First, break the working year up into chunks. It’s often simplest to start in weeks here, so your working year would be 52 weeks.
- Work out how many of those weeks you worked in the old pattern and how many in the new pattern
- Work out your holiday entitlement in hours for a whole year in the old and new patterns.
⦿ [number of hours per week in old pattern] X [5.6 weeks]
⦿ [number hours per week in new pattern] X [5.6 weeks]
- Pro rata those two totals - that means working out what proportion of the year each one applied for and dividing the total by that amount.
- Add the pro-rata totals together to get your total holiday hours for the year.
If you’re wondering how to convert annual leave hours into days again, you do this by dividing your leave hours totals by how many hours you work in a day. But it’s essential to divide the two totals separately because your daily hours have changed. So:
⦿ [total FT holiday hours] ÷ [hours you work per day FT] = [total FT holiday days earned]
⦿ [total PT holiday hours] ÷ [hours you work per day PT] = [total PT holiday days earned]
Here are a couple of examples.
Rhian moves from full-time to part-time
Rhian is changing from full-time (5 days a week) to part-time (3 days a week) at the start of April. She worked 40 hours a week full-time and will work 25 hours a week part-time.
- She breaks her working year up into 52 weeks.
- She’ll be working 12 weeks full-time and 40 weeks part-time.
- She works out her holiday entitlement in hours for the whole year for old and new patterns:
⦿ [40 hours] X [5.6 weeks] = 224 FT holiday hours
⦿ [25 hours] X [5.6 weeks] = 140 PT holiday hours
- She works out her holiday pro rata (dividing her whole-year totals into proportional amounts depending on how long she worked each pattern).
⦿ 224 [FT holiday hours] ÷ 52 [weeks in year] x 12 [weeks worked FT] = 51.7 hours
⦿ 140 [PT holiday hours] ÷ 52 [weeks in year] x 40 [weeks worked PT] = 107.7 hours
Rhian’s total holiday for the year is 51.7 + 107.7 = 159.4 hours.
Rhian wants to convert annual leave hours into days again. She goes back to her two separate FT and PT totals and divides each by the hours worked per day in each pattern.
⦿ 51.7 [FT holiday hours] ÷ [8 hours per day FT] = 6.5 [FT holiday days]
⦿ 107.7 [PT holiday hours] ÷ [5 hours per day PT] = 21.6 [PT holiday days]
Mohammed moves from part-time to full-time.
Mohammed is changing from part-time (4 days a week) to full-time (5 days a week) at the start of June. He worked 28 hours a week part-time and will work 35 hours a week full-time.
- He breaks his working year up into 52 weeks.
- He’ll be working 26 weeks full-time and 26 weeks part-time. That’s ½ a year each.
- He works out his holiday entitlement in hours for the whole year for old and new patterns:
⦿ [28 hours] X [5.6 weeks] = 156.8 holiday hours
⦿ [35 hours] X [5.6 weeks] = 196 holiday hours
- He works out his holiday pro-rata, dividing his whole-year totals in half because he worked half a year of each pattern:
⦿ 157 [holiday hours] ÷ 2 = 78.4 hours
⦿ 196 [holiday hours] ÷ 2 = 98 hours
Mohammed’s total holiday for the year is 79 + 98 = 176.4 hours.
(Want to know how those annoying decimal places actually work in terms of time on the beach? Jump here.)
What about irregular hours?
What happens if your working hours aren’t as straightforward as Rhian and Mohammed’s?
People who work irregular hours, or who do part-year work or have a zero-hours contract, are still entitled to a statutory 5.6 weeks paid holiday; it’s just worked out slightly differently. This keeps holiday entitlement fair across the board, whatever the terms of your contract.
Note that the rules changed on 31st March 2024. Here, we’re going to talk about the new rules that apply to leave years starting after this date. For irregular-hours workers, holiday hours are worked out at 12.07% of the hours worked in a pay period. A pay period is how often you get paid - a month or a week, for example.
So, if a zero-contract worker is paid monthly and does a total of 80 hours in January, they get 10 hours of paid holiday (rounded up from 9.6) for January.
Of course, they don’t have to take that holiday in January; they can save it up for a rainy August fortnight in Barry Island if they want. Workers on irregular hours accrue holiday, meaning they collect it as they work. Their accrued holiday is based on the time they’ve already worked.
Bear in mind that although zero-hour contracts are legal at the moment, they will soon be unlawful as of 2026 due to the Employment Rights Bill. Check out our Zero-Hour Holiday Pay Guide for more information.
Common conversion conundrums (and how to solve them)
Leave calculations can be complicated when you change the number of hours. Here are some common questions and their answers.
What happens about bank holidays?
UK employers don’t have to give bank holidays as paid leave (in other words, you may be required to work on a bank holiday.) However, an employer can choose to include bank holidays as part of the 5.6 weeks of statutory leave.
If an employer chooses to give bank holidays as part of statutory paid leave, then bank holiday entitlement for part-time workers is calculated pro-rata. For example, if a full-time worker works 40 hours a week and is entitled to 8 bank holidays a year, then a part-time worker at the same company working 20 hours a week would get 4 paid bank holidays.
To work out bank holiday entitlement when you change hours, you do a pro-rata calculation as above. Work out your total full-time bank holiday entitlement and your total part-time, then pro-rata those totals depending on how much of the year you work in each pattern.
Do I round up or down for partial days and hours?
Leave calculations often throw up pesky decimal points, and it can be hard to work out what this means in actual time off. (What is 0.125 of a day in actual hours on the sun loungers?!)
The rules are that employers can’t round down part days of a holiday, so you’re not going to lose those precious slivers of leisure time. In the first year of employment, employers must round partial days up to the nearest half day. It’s up to your employer whether they round them up after that. If you’re not sure, check your contract or ask your employer what their policy is.
Carrying over leave
What happens if you’ve accrued leave but haven’t yet taken the time off when you change hours mid-year?
You are still entitled to take that leave after your hours change. Leave you’ve already accrued is not affected by the hours’ change. Do the leave calculation as above and carry over the pro-rata leave accrued before the change.
How to avoid leave calculation problems
Employers and employees are all human, and leave calculations can be complicated and stressful, so the best advice is to maintain clear communication between HR/payroll and employees.
- Have a clear Annual Leave Policy in place.
- Regularly remind employees of leave policies and encourage them to take the leave they’re entitled to.
- Maintain an up-to-date written statement of employment particulars for every employee and share it with them so they can easily check holiday policy and calculations.
- Make it easy for people to ask questions when they need clarification.
Why getting It right matters
Taking time off work is beneficial for everyone. Workers need to relax and recharge. For employers, it means a happy, energetic workforce.
That’s why it’s important to get leave calculations right. For employees, correct leave calculation means everyone gets their full, rightful entitlement, and no one feels short-changed or confused. For employers, correct calculations ensure legal compliance, prevent disputes, maintain morale, and simplify payroll and absence management.
Oi, leave over!
Getting a handle on leave conversion empowers employees and simplifies HR management. What’s not to love? OK, we could all probably do without the calculations, but remember you can speak to your HR team or use a reliable online calculator like this one from the UK government to make sure your calculation is correct.
And don’t be afraid to raise concerns. We believe that no one should be ashamed or worried about making sure their annual leave is right and fair. Time off is your legal right and essential to mental and physical wellbeing.
So once you’ve sorted that holiday, make sure you enjoy it!
