First, decide which four-day week you run
“Four-day week” covers three quite different arrangements. Holiday works differently in each.
| Model | What changes | How to count holiday |
|---|---|---|
| Compressed hours | Same weekly hours and pay, worked over four longer days. For example, 37.5 hours as four 9.375-hour days. | Count in hours. The entitlement is the same as a full-timer’s: 5.6 × 37.5 = 210 hours. |
| Reduced hours, same pay | Fewer hours for the same pay, usually tied to keeping output up. | Depends on the contract. If contracts change to four days, the legal minimum becomes 5.6 × 4 = 22.4 days. |
| Reduced hours and pay | A part-time contract: four days for four days’ pay. | Pro rata, exactly as for part-time staff: 22.4 days minimum, more if your full-time allowance is higher. |
Compressed hours: count in hours, not days
Someone on compressed hours still works a full-time week, so they get the same holiday as a full-timer. The simplest fair method is to hold their allowance in hours.
- Allowance in hours = 5.6 × weekly hours. For 37.5 hours a week, that is 210 hours.
- When they take a day off, deduct the hours they would have worked that day, here 9.375.
- 210 ÷ 9.375 = 22.4 of their longer days. That is still 5.6 weeks off.
If your full-time allowance is higher than the legal minimum, convert it the same way: 33 days of 7.5 hours is 247.5 hours, or 26.4 days of 9.375 hours.
The common mistake: keeping the count in days
Most leave spreadsheets count days. On a four-day week that goes wrong in both directions.
- Give a four-day worker 28 days and they get 7 weeks off, not 5.6 (28 ÷ 4 = 7).
- Give someone on compressed hours 22.4 standard 7.5-hour days and they get 168 hours, which is 42 hours short of their 210.
Decide whether each person’s allowance is held in days or hours, write it in your policy, and use the same unit when they book time off.
Reduced hours: check the contract
Where people work fewer hours for the same pay, holiday follows the working week in their contract. If the contract now says four days, the legal minimum is 22.4 days and a higher contractual allowance is pro-rated the same way (for example 33 × 4 ÷ 5 = 26.4 days). If you run the four-day week informally on top of a five-day contract, the contract’s allowance still applies unless you agree a change. Either way, say which in writing before the first leave year starts.
A fixed day off or staggered days off
- Fixed day off, such as every Friday: simple to run, but most bank holidays fall on a Monday, so a team that takes Mondays off would never benefit from them unless you pro-rate.
- Staggered days off: keeps cover across five days, but people’s non-working days differ, so the team needs to see who is off on which day, and why.
Show non-working days separately from leave. A day someone never works is not a day of holiday, and mixing the two is how allowances drift.
Bank holidays
There is no legal right to have bank holidays off, but if your allowance includes them, pro-rate them rather than giving people only the ones that land on their working days.
Example: with 8 bank holidays a year, a four-day worker gets 8 × 4 ÷ 5 = 6.4 days. Someone on compressed hours gets the same hours as a full-timer: 8 × 7.5 = 60 hours, which is 6.4 of their 9.375-hour days. When a bank holiday falls on a day they work, they book it from that allowance.
Running a trial
- Set start and end dates, and say what happens to holiday if the trial ends early.
- If someone’s working week changes part-way through a leave year, work out the allowance for each part of the year separately.
- Holiday already taken stays taken. Recalculate what is left from the day the pattern changes.
Policy checklist
- Which model you run: compressed hours, reduced hours with the same pay, or reduced hours and pay.
- Whether allowances are held in days or hours, for each kind of contract.
- How bank holidays are counted.
- How part days are rounded. You must never round down, and in the first year of employment part days are rounded up to the nearest half day.
- Who approves changes to someone’s working week, and from what date.
- How you keep records. Since 6 April 2026, employers in Great Britain must keep adequate records of annual leave, carried-over leave and holiday pay for six years.
Check one person’s figures
The free pro-rata holiday calculator works out an allowance in days and hours from the days and hours someone works. For part-time contracts, see how to work out pro-rata holiday for part-time staff.
In Workframe, each person has a working pattern with their hours for every morning and afternoon, and a start date, so a trial or a change of pattern stays on record. Non-working days show separately from leave on the team view. Allowances are worked out from each person’s pattern in hours, shown in days when every working day is the same length and in hours when it is not, and bank holidays are pro-rated so a team that never works Fridays, or always takes Mondays off, is treated fairly. How Workframe handles holiday entitlement.