A 4-day week for a 10% pay cut: the maths
Dropping to four days for 10% less pay costs £45 a week after tax — and buys back 340 hours a year. The engine scores this one a genuine coin-toss, which is exactly why it is worth running with your own numbers.
The worked example
£40,000 over five days (37.5 hours) against £36,000 over four (30 hours) — same employer-style package, Plan 2 and 5% pension, hybrid with the same commute pattern:
Five days — £40,000
37.5 hrs/week
Four days — £36,000
30 hrs/week · −10% pay
A 10% pay cut is only a 5.9% take-home cut — the deduction stack works in your favour on the way down. £2,360 a year buys back 340 hours, and your hourly rate rises from £16.57 to £18.88: you are selling fewer hours at a better price.
The verdict: a genuine coin-toss
Money axis −0.93; the 340 hours saturate most of the time score at +3.4; with every priority equal the combined verdict is −0.12: 'too close to call'. This is the rare scenario the engine refuses to call for you — because it genuinely hinges on your weights. Nudge free time above money and it flips to switch; value money more and it says stay. No other number on this page matters as much as which of those people you are.
Two practical checks before you ask for it: pension — both contributions usually drop with salary (about £200 a year of combined contributions here), which compounds; and scope — a four-day week with a five-day workload is a 10% pay cut for the same job, which the wellbeing rating should hear about. Related: the remote version of this trade.
Run this scenario with your own numbers
The button opens the calculator pre-loaded with this exact worked example — change anything, including the ratings and your priorities, and every figure recomputes live, in your browser. Nothing you type is uploaded.