4-Day Week Calculator
Pro-rata: salary cut to 4 days. Compressed: same salary, longer days.
Your free day "costs" (take-home given up)
Net drop: £6,840/year (£570/month) vs gross drop £10,000
You keep 68.4% of the salary you give up (rest is tax/NI/pension/SL savings).
5-day take-home
£37,721
/year
4-day take-home
£30,881
/year
Net per day (5-day)
£145
Net per day (4-day)
£148
| 5-day | 4-day | Change | |
|---|---|---|---|
| Gross | £50,000 | £40,000 | -£10,000 |
| Income Tax | £6,984 | £5,084 | -£1,900 |
| NI | £2,794 | £2,034 | -£760 |
| Pension | £2,500 | £2,000 | -£500 |
| Take-home | £37,721 | £30,881 | -£6,840 |
1. Current salary: Enter your full-time (5-day) gross annual salary.
2. Scenario: Pro-rata models a 20% pay cut for 4 days (or custom %). Compressed hours keeps the same salary over 4 longer days.
3. Optional: Add pension, student loan, and tax region for accurate take-home. Use advanced options for tax code, gift aid, second job, etc.
4. Result: See how much take-home you give up for a free day (pro-rata) or how your per-day and per-hour rate changes (compressed).
Why Gross Drop Isn't Net Drop
When you switch to a pro-rata 4-day week, your gross salary typically drops by 20%. But the amount you lose from your bank account is less than 20% of your current take-home, because you also pay less Income Tax, National Insurance, pension and student loan on the reduced salary.
The calculator shows the "effective cost of your free day" — the actual take-home you give up per year. That number is what you should weigh against the value of an extra day off.
The £100k–£125k Zone: A Quirk for 4-Day Workers
If your full-time salary sits between £100,000 and £125,140, you are in the Personal Allowance taper — often called the "60% tax trap". For every £2 you earn above £100k, you lose £1 of Personal Allowance. Reducing your salary by going 4-day can recover some or all of that allowance, so the net cost of your free day can be lower than you'd expect from a simple 20% cut.
Use the calculator to see your exact net drop and consider pension salary sacrifice if you want to stay full-time but reduce the effective tax rate.
Compressed Hours: Same Pay, Different Rhythm
With compressed hours, you keep your full salary and work it over 4 longer days. Your take-home doesn't change — the calculator shows how your net per working day and net per hour change. Many people find that the lifestyle gain of a full day off outweighs the longer days, especially when total hours are similar or slightly lower.
Example: Pro-rata 4-day
Approximate. Use the calculator for your exact figure.
Related Tools
Common Questions
Is 80% pay standard for 4 days?
Many employers offer 80% (pro-rata) for 4 days. Some negotiate a different percentage. Use the calculator to set any % and see the net impact.
Does student loan change the cost?
Yes. With a pro-rata cut, your student loan repayment falls too, so the net drop in take-home is less than it would be without a loan. Add your plan in the calculator for an accurate result.