Four-Day Week UK: What the Big Trial Proved

The four-day week usually gets filed under "nice idea, never going to happen" in the same drawer as flying cars and an honest energy bill. Then in 2022 the UK ran the largest trial of it anywhere in the world, and the results came back so boringly positive that the sceptics had to change the subject rather than the policy.

This is not a fringe wellness story. It is the most rigorous test yet of an idea that sits right next to everything this site argues about money and time, and the headline finding is awkward for anyone who insists five days is the natural order of things. The companies mostly kept it.

The reframe: a four-day week is FIRE in instalments

Start with what the four-day week is really about, because it is not "working less". It is buying back time.

That is the exact same trade at the heart of financial independence. The FIRE saver spends a decade or two overfunding their freedom so they can reclaim all of it in one go, at 50 or 55. The four-day week reclaims a slice of it now, every single week, while you are still building the pot. Same currency, different schedule. One is freedom in a lump sum, the other is freedom in instalments.

Seen that way, the four-day week works with saving hard for early retirement rather than against it. It is the pressure valve that stops you burning out before you get there. If your only plan for escaping a job you cannot stand is to grind for fifteen more years, you are betting your health on the finish line, and that is a bet plenty of people lose.

What the trial actually found

The numbers are the point, so here they are. The pilot ran from June to December 2022, organised by researchers at Boston College, the University of Cambridge and the think tank Autonomy. Sixty-one companies and around 2,900 workers took part. The model was what campaigners call 100:80💯 keep 100% of pay, drop to 80% of the hours, in exchange for maintaining 100% of output.

That last condition matters. Nobody was promised a day off for nothing. The deal was a genuine productivity bet: cut a day, keep the results.

When the results landed, they were lopsided.

• 71% of staff reported reduced burnout, and 39% said they were less stressed.
• Anxiety, fatigue and sleep problems all fell. Mental and physical health both improved.
• Resignations dropped by 57% over the trial compared with the same period a year earlier. People stop leaving jobs that give them their lives back.
• Revenue barely moved, rising 1.4% on average across the firms that reported figures. The work still got done.

And the verdict that actually counts, the one from the businesses paying the bills: of the 61 companies, 56 carried on with the four-day week after the trial ended. A year later, at least 54 were still running it and 31 had made it permanent. These were ordinary firms that ran the experiment, looked at their own numbers, and decided five days had been costing them more than it earned.

The catch, because there is always one

Honesty demands the other side. A 1.4% revenue bump across a self-selecting group of companies that volunteered for a four-day-week trial is not proof that every business can do this. Firms that signed up were already sympathetic, already willing to redesign how they work. The corner shop, the A&E department, the building site: not all of them compress into four days, and pretending otherwise helps nobody.

There is also a quieter risk worth naming. "100% of output in 80% of the time" can mean two very different things. The good version is cutting the dross: fewer pointless meetings, less status-update theatre, tighter focus. The bad version is the same workload crammed into four days, with people skipping lunch and answering email on the day off. The first is a genuine productivity gain. The second is just intensification with a nicer label, and it can quietly hand back every wellbeing gain the trial measured.

So the four-day week is not a free lunch. It is a trade that works when an organisation is willing to ruthlessly delete low-value work. Where managers refuse to do that, a four-day week becomes a four-day cram, and the burnout it was meant to fix comes straight back.

Is the UK getting a four-day week?

For all the positive data, there is no national four-day week policy in Britain, and there is unlikely to be one soon. The change is happening employer by employer, not by law.

A few public bodies have pushed ahead anyway. South Cambridgeshire District Council became the first UK council to trial a four-day week for staff, and central government pushed back hard, telling councils to drop it. That tug of war tells you where the politics sits: the evidence is running ahead of the willingness to act on it. It is the same instinct that keeps a universal basic income stuck at the debating-society stage. Both ideas loosen the link between hours worked and money earned, and that link is one the system guards closely.

Which leaves it down to you and your employer. The practical move is to know the difference between a reduced-hours four-day week (32 hours, full pay, the thing the trial tested) and a compressed-hours four-day week (40 hours squeezed into four longer days, same pay, same total work). The first buys you time. The second just rearranges it, and for some people the ten-hour days are worse than five normal ones. When you negotiate, be clear about which one you actually want.

The deeper lesson from the trial is the one the spreadsheet keeps confirming across this whole topic: time is the asset, money is just the tool for buying it back. The four-day week is a reminder that you do not have to wait until you are retired to start spending it.

Frequently Asked Questions

Does a four-day week mean a pay cut?

In the model the UK trial tested, no. The 100:80:100 deal kept pay at 100% while cutting hours to 80%, with the trade being that output had to hold steady. That is what makes it different from simply going part-time. A genuine four-day week is full pay for fewer hours; part-time is less pay for fewer hours. If an employer offers you four days at four-fifths of your salary, that is part-time work with a fashionable name.

Did productivity really hold up?

Across the trial, yes. Company revenue rose 1.4% on average among firms that supplied data, and the overwhelming majority of companies chose to keep the policy after seeing their own results. The mechanism is usually cutting low-value work rather than working faster. The honest caveat is that participating firms self-selected and were office-based knowledge businesses for the most part, so the result does not automatically transfer to every sector.

What are the disadvantages of a four-day week?

The main risk is intensification: the same workload crammed into four days, which hands back the wellbeing gains the trial measured. It also does not fit every sector, since shift-based and customer-facing roles like A&E or retail are harder to compress. And a reduced-hours week can slow wage growth over time. The 2022 trial worked because firms deleted low-value work rather than simply speeding people up.

How does a four-day week fit with saving for FIRE?

They pull in the same direction more than people assume. FIRE is about buying back your time with money; a four-day week buys some of that time back immediately. If a shorter week keeps you in a career you can actually sustain, it can mean more years of earning and investing rather than a sudden flameout. The trade-off is that lower hours can mean slower wage growth, so it works best once your savings rate and core investments are already established.

Can I ask my employer for a four-day week?

You can, and in the UK you have had the right to request flexible working from day one of a job since April 2024. A request is not a guarantee, and the employer can refuse on specific business grounds, but the trial gives you something to point at. Frame it as a productivity proposal, not a favour: name the low-value work you will cut, and ask to run it as a time-limited trial with agreed output measures, which is exactly how the successful companies started.