Four Day Week Calculator
Updated November 2026 · Free · No sign-up
Calculate what a 4-day week means for you or your team — the compressed 4/10 version vs the true 100-80-100 model (full pay, 80% hours, maintained output), with the savings both sides bank.
Quick answer: Two different animals: 4/10 compression keeps 40 hours (same pay, longer days — see the compressed calculator); the true 4-day week is 100% pay for 80% time against 100% output — trial data shows output holds via meeting and focus discipline, while employees bank a commute day + childcare day.
The Three "4-Day Weeks"
| Model | Hours | Pay | The deal |
|---|---|---|---|
| 100-80-100 | 4×8 = 32 | 100% | Output maintained via efficiency — the trial-validated version |
| Compressed 4/10 | 4×10 = 40 | 100% | Same hours, reshaped — daily-OT traps apply |
| Pro-rata 80% | 4×8 | 80% | Part-time by another name — fine, but not the headline model |
What the Trials Actually Found
The large UK pilot (61 firms) and successors: revenue flat-to-up, resignations down ~57%, burnout sharply down, and ~90%+ of firms continuing. The mechanism is not magic — it’s recovered meeting time, protected focus blocks, and process pruning; the firms that failed skipped that redesign. Coverage roles (support, clinical) need staggered fifth-day coverage, which costs real headcount — the honest limit of the model.
Worked Example — Employee Side
$70k, 100-80-100, $40/day of commute+childcare: pay unchanged, 48 days/year freed, direct savings ~$1,920 + ~250 reclaimed hours. Equivalent raise ≈ $9-11k of value at zero salary cost — the retention math employers are quietly buying.
Making the Employer Case
Pitch sequence: (1) price current meeting load and propose the cuts that fund the day; (2) 3-month pilot with output metrics agreed UP FRONT (baseline first); (3) staggered days for coverage (team splits Mon/Fri); (4) measure resignations/absence against the turnover cost baseline. The argument is never “less work” — it’s buying output discipline with time.
Frequently Asked Questions
What is the 100-80-100 model?
100% pay for 80% of the time against 100% of output — the definition used by the major 4-day-week trials, distinct from compressed 40-hour weeks.
Do 4-day weeks cut pay?
Not in the 100-80-100 model; pro-rata 80% arrangements do — know which deal is on the table before celebrating.
Did the 4-day week trials work?
Largely: maintained revenue, large burnout and resignation drops, and most pilot firms made it permanent — with meeting/process redesign as the common success factor.
What jobs struggle with 4-day weeks?
Coverage-bound roles (support, healthcare, retail) — the fifth day needs staffing, which means staggering or hiring, the model’s real cost frontier.
How much is the free day worth to an employee?
Commute + childcare savings plus ~48 reclaimed days a year — commonly $8-12k of annual value at median costs, untaxed because it never becomes income.
✓ Formula verified • Last updated: November 3, 2026