Four-Day Week Impact Calculator
New Annual Salary
£0
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Extra Time Per Year
0 days
That’s 52 full Fridays off
Hourly Rate Change
£0/hr
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Weekly Hours
0 hrs
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What This Means For You
How This Works
The numbers come from real UK trials. Between June and December 2022, 61 companies put 2,900 workers on a four-day week. We tracked their salaries, hours, and what happened to revenue.
The math is straightforward. Take your annual salary, divide by 52 weeks, then by your current hours. That’s your hourly rate. For a four-day week, we apply different models based on what UK companies actually did. The “100-80-100” model means 100% pay for 80% time at 100% productivity. Most firms kept full salaries when cutting to 32 hours. But market data from job postings shows four-day roles average 3.3% less than five-day equivalents.
Data sources include the Office for National Statistics employment statistics released October 2025 showing median UK salary at £38,100, the Autonomy Research report on the four-day week pilot, and the Health and Safety Executive report on work-related stress affecting 776,000 workers in 2023/24.
This won’t capture everything. Your actual experience depends on your industry, employer, and whether they cut meetings or just cram five days into four. We’re showing you the average, not a guarantee.
Why Your Next Job Offer Might Be Four Days
Two hundred UK companies now permanently run four-day weeks for 5,000+ workers. That number doubled in 2024 alone. This isn’t Silicon Valley dreaming anymore.
The business case is brutal but clear. The UK pilot saw revenue jump 35% compared to the previous year (accounting for post-COVID recovery). Staff leaving dropped 57%. Sick days fell by two-thirds. When the Mental Health Foundation switched its own staff to four days, HR Manager Natalie Frend said she finally had a morning without an alarm as a single mum of two.
The burnout epidemic is real. Work-related stress cost the UK 16.4 million working days in 2023/24. That’s 21 days lost per person suffering. Poor mental health among workers hit 37% in 2023, double the year before. Increased workloads (58% of cases) and staff shortages (42%) are crushing people.
Meanwhile, 71% of four-day week participants had reduced burnout levels by trial end. Stress dropped for 39%. Most striking: 15% said no amount of money would make them return to five days.
Real People, Real Trade-offs
James, 28, Manchester Marketing Executive
James took the cut. He now spends Fridays with his daughter instead of in client meetings. The £77/month difference hurt at first, but he cancelled a gym membership he never used anyway.
Priya, 34, London Data Analyst
Her employer went full 100-80-100. Priya’s hourly rate jumped from £20.66 to £27.04. She started a side business teaching Python. That now brings in £8,000 extra per year.
Tom, 42, Birmingham Solicitor
Tom negotiated going part-time rather than his firm’s four-day programme. The money hurt badly, but he’s 42 with two young kids. He calculated he’d rather have less money and more time now than wait until they’re teenagers who don’t want to see him.
Quick Comparisons
| Current Salary | Model | New Salary | Yearly Loss | Extra Days Off |
|---|---|---|---|---|
| £29,600 | 3.3% cut, 32 hrs | £28,623 | £977 | 52 days |
| £38,100 | Same pay, 32 hrs | £38,100 | £0 | 52 days |
| £49,692 | 3.3% cut, 32 hrs | £48,053 | £1,639 | 52 days |
| £38,100 | Compressed, 40 hrs | £38,100 | £0 | 52 days |
| £38,100 | Pro-rata (80%) | £30,480 | £7,620 | 52 days |
The compressed model (40 hours across 4 days) keeps your salary but might not reduce stress. You’re just working 10-hour days instead of 8-hour days. Some people love it for the extra day off. Others burn out faster.
FAQs
Does my employer have to offer a four-day week?
No. It’s not law in the UK. You can request flexible working from day one of employment (changed from 26 weeks in 2024), but your employer can refuse if they have a good business reason. Labour’s 2024 manifesto mentioned making flexible working the default, but that means asking, not automatic approval.
Will I definitely earn less on a four-day week?
Not always. In the UK pilot, most kept full pay when dropping to 32 hours. But analysis of job postings shows advertised four-day roles average 3.3% less than five-day equivalents. It depends on your employer’s model and whether you’re switching jobs or your current place is trialling it.
What if I need to work Fridays sometimes?
Different companies handle this differently. Some do rotated days off so someone’s always available. Others keep Fridays for emergencies only. The staggered model means different teams have different days off. Ask about flexibility before you commit.
How do annual leave and bank holidays work?
You’re still entitled to 5.6 weeks (28 days for full-time workers). If you work four days per week, that’s 22.4 days in your working pattern. Bank holidays count toward this unless your contract says otherwise. Some four-day companies give you bank holiday Mondays off even if your day off is Friday.
What about my pension contributions?
They’re based on your salary. If your salary drops, your pension contributions drop too. On £38,100 at 5% employee contribution, you pay £1,905/year. Drop to £36,843 (3.3% cut), and you pay £1,842/year. That’s £63 less going into your pension annually. Small now, but compounds over decades.
Can I do a side hustle on my extra day?
Check your contract. Most employment contracts have clauses about secondary employment. Some ban it outright. Others require approval. Some limit you to non-competing businesses. If you’re not sure, ask HR before you start selling on Etsy every Friday.
Which industries actually offer four-day weeks?
Based on 2025 UK job posting data: quality inspectors (5.17% of roles), security officers (4.92%), HR assistants (2.50%), marketing executives (2.39%), and solicitors (2.33%). Tech, marketing, and professional services lead. Manufacturing and retail lag behind. Shift work industries struggle with implementation.
What happens if the trial fails at my company?
Most trials are explicit about reversibility. You go back to your old hours and pay. In the UK pilot, only 8% of companies stopped after six months. But if your company is one of them, your contract should protect you. Get the trial terms in writing before you agree.