Work out statutory holiday entitlement
Full year, new joiners, leavers and bank holidays, for any working pattern.
Almost every UK worker is entitled to 5.6 weeks of paid holiday a year, capped at 28 days for a five-day week, yet the figure changes for anyone who works part time or joins partway through the leave year ([1]). A three-day-week worker is owed 16.8 days, not 28, and a full-time employee who starts in the seventh month of the leave year accrues barely half the annual allowance ([2]). Pro rata calculation is where these numbers are worked out.
Getting the proration wrong is one of the most common payroll errors an employer makes. Under-crediting a part-time worker's leave breaches the Working Time Regulations, while over-crediting quietly inflates the wage bill and creates a payment in lieu the business never planned for ([3]). The stakes rise at termination, when accrued but untaken statutory leave must be paid out in cash ([4]).
This guide sets out how pro rata holiday works in each situation: part-time patterns, mid-year starters, leavers and the treatment of bank holidays. It covers the days-based and hours-based methods, the first-year accrual rule, the rounding conventions and the exact formula used at the end of employment.
Key takeaways
- The statutory baseline is 5.6 weeks' paid leave a year, capped at 28 days, and every pro rata figure derives from it.
- A part-time worker on set days gets 5.6 multiplied by the days worked each week, so a four-day week earns 22.4 days.
- In the first year, regular-hours staff accrue one-twelfth of the annual entitlement at the start of each month.
- Fractions of a day are rounded up, never down, in the first year of employment.
- When a worker leaves, unused statutory leave is paid in lieu, pro-rated to the portion of the leave year worked.
- Bank holidays are not a separate legal right, so an employer may count them towards the 5.6 weeks.
What pro rata holiday actually means
Pro rata is Latin for "in proportion", and in a payroll context it means scaling the full-time holiday allowance down to match a worker's actual working pattern or their length of service in the leave year. The principle rests on a single statutory floor that applies to almost all workers, from which every reduced figure is calculated ([5]).
The 5.6-week baseline and the 28-day cap
The Working Time Regulations 1998 give almost all workers 5.6 weeks of paid annual leave, a figure that has applied since 2009 and covers employees, agency workers and those on zero-hours and irregular contracts alike ([6]). For someone working five days a week, 5.6 weeks equals 28 days, which is also the statutory maximum: an employee working six days a week is still entitled to only 28 days, not 33.6 ([7]).
That cap matters for proration because it changes the arithmetic at the top of the scale. Below five days a week the entitlement scales cleanly with the pattern, but at six days or more it flattens out at 28. The 28-day ceiling is a statutory limit under the Regulations, so no proration method can push a worker above it ([8]).
Statutory leave versus contractual leave
The 5.6 weeks is a minimum, and many employers offer more as a contractual benefit. Proration rules bite hardest on the statutory portion, because that is the part protected by law; anything above it is governed by the contract of employment ([9]). An employer can attach conditions, such as a qualifying period of service, only to the contractual excess, never to the statutory minimum, which begins to accrue from the first day of employment ([10]).
This distinction shapes the whole calculation. When a business prorates leave for a part-time or mid-year worker, it must at least deliver the statutory 5.6 weeks in proportion, and it should be clear in the contract how any enhanced allowance is prorated too ([11]). Confusing the two tiers is a frequent source of disputes that reach an employment tribunal.
Pro rata holiday for part-time workers
A part-time worker who works the same pattern every week has the simplest proration. The method depends on whether leave is tracked in days or in hours, and picking the right one keeps the figures consistent across a mixed workforce.
The days-based method
For a worker on a fixed number of days each week, the entitlement is 5.6 multiplied by the number of days worked ([12]). A four-day week gives 22.4 days, a three-day week gives 16.8 days and a two-day week gives 11.2 days. The official worked example on GOV.UK uses exactly this method: a worker on three days a week is entitled to at least 16.8 days' leave, calculated as 3 multiplied by 5.6 ([13]). The table below shows the full scale.
| Days worked per week | Statutory leave (5.6 x days) |
|---|---|
| 5 days | 28 days |
| 4 days | 22.4 days |
| 3 days | 16.8 days |
| 2 days | 11.2 days |
| 1 day | 5.6 days |
| 6 days | 28 days (capped) |
Those fractional days are genuine entitlement rather than a rounding artefact, and the employer must either allow them to be taken or convert them into hours so no leave is lost ([14]). Getting this arithmetic embedded in a reliable payroll process for SMEs removes the risk of a manual miscalculation each time a working pattern changes.
The hours-based method
Where a worker's days vary in length, tracking leave in hours is more accurate than counting days. The calculation multiplies the hours worked each week by 5.6, so a worker doing 20 hours a week is entitled to 112 hours of paid holiday a year ([15]). Managing leave in hours avoids the distortion that arises when a "day" of holiday means four hours for one shift and nine for another.
The hours-based method also travels better across the workforce, because it puts full-time and part-time staff on the same unit of account ([16]). A full-time worker on 37.5 hours a week would accrue 210 hours of statutory leave a year, and comparing 112 hours against 210 hours is more transparent than comparing part-days ([17]). The GOV.UK holiday entitlement calculator accepts either days or hours and shows the working, which is a useful cross-check ([18]).
Pro rata holiday for mid-year starters
A worker who joins after the leave year has begun does not receive the full annual allowance immediately. Instead, statutory leave builds up over the remainder of the year, and the mechanism is set out in official guidance.
The first-year accrual rule
During the first year of employment, a worker accrues leave at one-twelfth of their full annual entitlement at the start of each month, rounded up to the nearest half day ([19]). For a five-day-week worker with the full 28-day allowance, one-twelfth is 2.33 days, which rounds up to 2.5 days credited at the start of each month ([20]). Starting partway through a month still earns that whole month's twelfth, because accrual is credited at the start of the month rather than day by day.
The table below shows how the allowance for a full-time, five-day-week starter builds across a leave year, before rounding.
| Full months remaining in leave year | Accrued statutory leave (of 28 days) |
|---|---|
| 12 | 28 days |
| 9 | 21 days |
| 6 | 14 days |
| 3 | 7 days |
| 1 | 2.33 days (rounds to 2.5) |
The rounding-up rule applies only in the first year of employment; after that, an employer may round part-days up but is not obliged to ([21]). Because the one-twelfth method depends on when the leave year starts and when the worker joined, it is worth confirming each new starter's figure at onboarding rather than assuming a flat pro rata fraction.
Combining part-time and mid-year proration
Where a new starter is also part time, the two prorations stack. The employer first works out the part-time annual figure using the days-based or hours-based method, then applies the one-twelfth monthly accrual to that reduced figure ([22]). A three-day-week worker with a 16.8-day annual entitlement who joins with six full months left in the leave year accrues half of 16.8, giving 8.4 days before rounding.
This is where manual spreadsheets tend to fail, because the order of operations and the rounding both have to be right ([23]). Accountants managing this across dozens of clients typically rely on a payroll bureau platform that applies the statutory method per scheme, so the calculation is consistent whatever the working pattern.
Pro rata holiday when a worker leaves
At the end of employment, any statutory leave a worker has accrued but not taken must be paid in cash. This payment in lieu is one of the few points at which unused holiday can lawfully be converted to money ([24]).
The payment in lieu calculation
The Working Time Regulations require an employer to calculate accrued but untaken statutory holiday at termination and pay it, whether the worker resigns, is made redundant or is dismissed ([25]). The proration counts the days employed in the leave year as a fraction of the whole year, applies that fraction to the annual entitlement, then subtracts any leave already taken ([26]). A full-time worker who leaves 90 days into a January-start leave year having taken two days is owed roughly 28 multiplied by 90 divided by 365, less 2, which is about 4.9 days' pay.
Entitlement at termination may be rounded up but never down, and accrued statutory leave must still be paid even where the worker is dismissed for gross misconduct ([27]). The cash value of each day is a day's pay, calculated using the same rules that govern holiday pay during employment ([28]). For workers with variable pay, that means the 52-week average method covered in the guide to the 52-week holiday pay reference period.
Overtaken leave and clawback
The mirror problem arises when a worker has taken more leave than they had accrued by their leaving date. Recovering the overpayment is only lawful where the contract, or a separate written agreement, expressly permits a deduction from final pay for holiday taken but not accrued ([29]). Without that clause, the employer generally cannot claw the value back.
This makes the leaving-date proration a two-way calculation, not simply a payment. Running the figure early in a notice period lets the employer decide whether to require the balance of leave to be taken before the last day, which is often cleaner than a final-pay adjustment ([30]).
Bank holidays and pro rata entitlement
There is no automatic legal right to paid time off on the eight bank holidays in England and Wales; they are treated as ordinary working days unless the contract says otherwise ([31]). An employer may include bank holidays within the 5.6-week statutory allowance or grant them on top, and the contract should state which approach applies.
For part-time workers, the treatment of bank holidays is a common source of unfairness. Because most bank holidays fall on a Monday, a part-time worker who never works Mondays could miss out entirely, while a colleague who always works Mondays loses several days of their allowance to them ([32]). The usual fix is to give part-time staff a pro rata bank holiday allowance regardless of the days they work, added to their leave pot to draw down as they choose. The Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000 make it unlawful to treat part-time staff less favourably than comparable full-timers, which is the legal driver behind that approach ([33]).
Work out any pro rata figure in seconds
Rather than run the days, hours and monthly accrual arithmetic by hand for every worker, an employer can size the entitlement instantly with the Moonworkers holiday entitlement calculator, which applies the statutory 5.6-week rules to any working pattern or start date.
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Conclusion
Pro rata holiday is not a single calculation but a family of them, each anchored to the same 5.6-week statutory floor and 28-day cap. The right method depends on the question being asked: days multiplied by 5.6 for a settled part-time pattern, hours multiplied by 5.6 where shifts vary in length, one-twelfth a month for a new starter, and a days-in-year fraction at termination. In every case the statutory minimum sets the floor and the contract governs anything above it.
The wider direction of travel is towards automation of exactly this kind of rules-based arithmetic. As more HR and workforce platforms embed UK payroll compliance directly into their own products, the pro rata calculation moves from a manual spreadsheet task to a function that runs the moment a working pattern or a leaving date is entered, which is where the risk of a costly miscalculation finally disappears.
Frequently asked questions
How do I calculate pro rata holiday for a part-time worker?
Multiply 5.6 by the number of days the worker works each week, up to the 28-day cap. A four-day week gives 22.4 days and a three-day week gives 16.8 days ([34]). Where shift lengths vary, multiply the weekly hours by 5.6 instead, so 20 hours a week produces 112 hours of annual leave.
How is holiday prorated for someone who starts partway through the year?
In the first year of employment, leave accrues at one-twelfth of the full annual entitlement at the start of each month, rounded up to the nearest half day ([35]). A full-time starter with six full months left in the leave year accrues 14 days of the 28-day annual allowance.
Is pro rata holiday rounded up or down?
During the first year of employment, part-days are rounded up to the nearest half day and never down ([36]). After the first year, an employer may choose to round part-days up but is not legally required to, so the contract should make the policy clear.
What happens to unused pro rata holiday when someone leaves?
Any accrued but untaken statutory holiday is paid in lieu in the final wage, prorated to the days employed in the leave year less any leave already taken ([37]). The cash value is a day's pay for each day owed, using the same rules that apply to holiday pay during employment, and the figure may be rounded up but not down.
