The four-day week is having a moment — but not every four-day week means the same thing for your pay. Some employers offer it on full pay (compressed hours); others offer it pro-rata, meaning you earn 80% of the full-time salary. A 4 day week pro rata salary calculator sorts out the second kind: the genuine part-time arrangement where your pay is scaled to the days you work.
This guide covers exactly how pro-rata four-day-week pay is worked out, with tables and examples you can check against your own contract. (If your employer is offering four longer days for full pay, that’s a compressed-hours arrangement — different maths, same number of days in the office.)
The Basic Calculation: 0.8 FTE
A pro-rata four-day week is 4 ÷ 5 = 0.8 FTE — you work 80% of full-time hours and earn 80% of the full-time salary.
The formula:
Your salary = Full-time salary × 0.8
On a £40,000 full-time salary, a four-day week pays £32,000. On £28,000, it pays £22,400. On £55,000, it pays £44,000.
As with any pro-rata calculation, the day-count shortcut only works if your working days match the length of a full-timer’s days. If full-time is 37.5 hours over five 7.5-hour days and you work four 7.5-hour days (30 hours), the fraction is 30 ÷ 37.5 = 0.8 — the same answer. But if you work four 9-hour days (36 hours), your fraction is 36 ÷ 37.5 = 0.96, which is barely a pay cut at all. Always verify with hours, not just days.
Worked Example: £42,000 Down to Four Days
Daniel earns £42,000 working full-time, 37.5 hours a week. He agrees a four-day week, working Monday to Thursday, 7.5 hours a day.
Step 1: Confirm the hours.
4 days × 7.5 hours = 30 hours a week.
Full-time: 37.5 hours.
Fraction: 30 ÷ 37.5 = 0.8.
Step 2: Calculate the salary.
£42,000 × 0.8 = £33,600 a year.
Step 3: Monthly and hourly.
Monthly: £33,600 ÷ 12 = £2,800.
Hourly: £33,600 ÷ (30 × 52) = £33,600 ÷ 1,560 = £21.54 an hour — identical to the full-time hourly rate of £42,000 ÷ 1,950 = £21.54. The hourly rate doesn’t change; only the total does.
Step 4: Sanity-check the take-home.
At £33,600, Daniel stays comfortably inside the basic-rate tax band. His approximate take-home is around £27,000 a year, or £2,250 a month — a useful figure to have before agreeing to the change.
4-Day Week Salaries at a Glance
Quick-reference table for a standard 0.8 FTE four-day week. For your exact hours, use our free pro rata salary calculator.
| Full-time salary | 4-day week salary (0.8 FTE) | Monthly (before tax) |
|---|---|---|
| £24,000 | £19,200 | £1,600 |
| £26,000 | £20,800 | £1,733 |
| £30,000 | £24,000 | £2,000 |
| £35,000 | £28,000 | £2,333 |
| £40,000 | £32,000 | £2,667 |
| £45,000 | £36,000 | £3,000 |
| £50,000 | £40,000 | £3,333 |
| £60,000 | £48,000 | £4,000 |
| £70,000 | £56,000 | £4,667 |
| £80,000 | £64,000 | £5,333 |
Pro-Rata 4-Day Week vs Compressed Hours: Don’t Mix Them Up
This is where most confusion happens, so let’s be precise:
Pro-rata four-day week (this article): You work 80% of full-time hours for 80% of full-time pay. A genuine part-time arrangement. Your contract changes, your salary drops, your holiday is pro-rated.
Compressed hours (full-pay four-day week): You work 100% of full-time hours squeezed into four longer days — for example, four 9.5-hour days instead of five 7.5-hour days. Your pay doesn’t change at all. Your contract’s hours don’t change, only their distribution.
The 100-80-100 model: Some high-profile trials (including the well-known UK pilot) tested 100% pay for 80% of the time with 100% productivity. That’s a company policy decision, not a calculation — there’s no pro-rating involved.
Why does the distinction matter? Because job adverts are often vague. An advert saying “four-day week available” could mean any of the three. Before you apply — or accept — ask: “Is the salary pro-rated, or is this compressed/full-pay?” The difference on a £40,000 role is £8,000 a year.
Holiday on a Pro-Rata 4-Day Week
Full-time minimum: 5.6 weeks × 5 days = 28 days (including bank holidays). On a four-day week:
5.6 × 4 = 22.4 days a year.
As with three-day weeks, the bank holiday question matters. If your day off is Friday, you’ll miss most bank holidays (which usually fall on Mondays) — meaning nearly all 22.4 days are yours to choose. If your day off is Monday, bank holidays will eat into your allowance, and you should check whether your employer tops it up with a pro-rated bank holiday addition.
Overtime and Extra Days
One practical wrinkle: if you regularly work a fifth day, how is it paid? Common approaches:
- Paid at your normal hourly rate up to full-time hours, then at overtime rates beyond that.
- Time off in lieu at the same rate.
- Counted toward a bonus threshold in some sales roles.
Whatever the arrangement, get it in writing. The most common dispute in four-day-week arrangements isn’t the base salary — it’s what happens when the “day off” quietly becomes a working day.
Is a 4-Day Week Worth the Pay Cut?
Only you can answer that, but the maths helps. A 20% pay cut buys back 20% of your working life — 52 extra days off a year. For many people, the effective “hourly rate of free time” is excellent value, especially since the tax system softens the blow: the £8,000 you give up on a £40,000 salary would mostly have been taxed at 20% plus 8% NI, so your actual take-home falls by roughly £5,760, not £8,000.
Counter-considerations: pension contributions fall in cash terms, some benefits (like bonuses or share schemes) may be pro-rated, and career progression can slow in some workplaces — though the evidence on that is mixed and improving.
What to Ask Before Accepting a 4-Day Role
Whether you’re negotiating down or applying fresh, pin these down before you sign:
- Which model is it? Pro-rata, compressed, or full-pay? Get it in the contract.
- Which day is off — and is it fixed? A floating day off is flexible but can be eroded; a fixed day is easier to protect.
- How are bank holidays handled? Especially if your day off is a Monday.
- What triggers overtime? Hours beyond your 4-day pattern, or beyond full-time hours? The answer changes your pay significantly.
- Can the arrangement be reviewed? A 6- or 12-month review clause protects both sides.
The Career Progression Question
The unspoken worry about four-day weeks is career impact. The honest picture: it varies enormously by employer. In workplaces where output is measured, part-timers progress at the same rate as full-timers doing equivalent work — the law requires equal treatment for promotion opportunities. In presence-driven cultures, visibility can suffer.
Practical defences: keep your day off genuinely free (constant availability trains people to ignore the boundary), make sure your objectives are pro-rated too (80% of the targets, not 100%), and document your achievements in the same way full-time colleagues do. If your objectives aren’t scaled to your hours, raise it at your next review — it’s one of the commonest part-time grievances and one of the easiest to fix.
The 4-Day Week and Your Mortgage Application
A practical point people discover late: mortgage lenders assess affordability on your current contracted salary. If you move from £40,000 to a £32,000 four-day arrangement and then apply for a mortgage, the lender uses £32,000 — which can meaningfully reduce what you can borrow.
If a house move is on the horizon, sequence matters. Some buyers complete their mortgage application before requesting reduced hours; others ask their employer to delay the contractual change until after completion. Lenders will ask for recent payslips, so the timing needs to be genuine — but there’s nothing improper about ordering life events sensibly. It’s worth a conversation with a mortgage adviser before you sign the hours variation.
Other working patterns: 20 hours a week · 24 hours a week · 30 hours a week · 37.5-hour week · 40-hour week · 2 days a week · 3 days a week · 37.5 vs 40 hours · part-time hours tables · pro rata hours · days vs hours · examples by days per week
FAQs
Is a 4-day week always 80% pay?
No. A pro-rata four-day week is 80% of full-time pay, but compressed-hours and 100-80-100 arrangements pay 100%. Always check which model a job advert means.
How many holiday days do I get on a 4-day week?
The statutory minimum is 22.4 days a year including bank holidays (5.6 weeks × 4 days). Your contract may be more generous.
Can I be forced onto a 4-day week with a pay cut?
Your employer can’t unilaterally cut your contracted hours and pay — that would be a breach of contract. Any move to a four-day week needs your agreement (or a proper contractual variation process).
Does a 4-day week affect statutory sick pay or maternity pay?
Statutory payments are based on your average weekly earnings, so a lower salary can reduce them. For statutory maternity pay, the key figure is your average earnings in the 8 weeks before the 15th week before your due date — timing a hours change around this window matters.
Run Your Own Numbers
Every four-day arrangement is slightly different — day lengths, bank holiday policies, overtime rules. Plug your exact hours into a free pro rata salary calculator and you’ll have the precise figure before you negotiate.