Analysis: the UK has run some of the world’s best-known four-day week experiments. Here is what they showed, and where the evidence is still thin.
What did the four-day week UK trials actually find? Across the main pilots, most participating employers kept the shorter week, staff reported less burnout and better wellbeing, and measured output or service performance generally held steady rather than falling. The catch is that the organisations volunteered, much of the evidence comes from surveys, and few trials compared participants with similar firms that kept a five-day week. The results show the model can work for some employers. They do not yet prove it would work across the whole economy.
What the four-day week UK trials tested
Most British pilots have used what campaigners call the 100:80:100 model: staff keep 100% of their pay, work 80% of their previous hours, and commit to keeping at least 100% of their output. That is different from compressed hours, where people squeeze five days of hours into four longer days. In a genuine four-day week, total hours fall.
Three sets of results dominate the UK debate: a large private-sector pilot in 2022, a smaller follow-up pilot that reported in 2025, and South Cambridgeshire District Council’s trial, the first in British local government.
The 2022 pilot: 61 companies and around 2,900 workers
The biggest UK trial ran from June to December 2022. It was organised by the campaign group 4 Day Week Global with the think tank Autonomy and the 4 Day Week UK Campaign, with researchers from the University of Cambridge and Boston College analysing the results. Sixty-one organisations took part, from marketing and finance to hospitality and online retail.
The headline findings, published in February 2023, were striking:
- 56 of the 61 companies said they would carry on with a shorter week, and 18 made the change permanent.
- 71% of employees reported lower levels of burnout.
- Sick days fell by about two-thirds and resignations dropped by 57% compared with a matching period.
- Revenue rose by 1.4% on average over the trial, weighted by company size.
- Only two firms said they had hired extra staff to keep output up.
Why sceptics urged caution
Critics did not dispute that participants were happier. They questioned what the numbers could prove. A review by the US employment law firm Constangy pointed out that around 70 firms signed up but nine dropped out, that only some of the remaining companies supplied business data, and that just 58% of employees completed the final survey. Firms that stayed in and responded may simply have been the ones having a good experience.
The same review noted that the reduction in working time was smaller than the label suggests: average weekly hours fell from about 38 to 34. And the 1.4% revenue increase came during a period when UK inflation was close to 10%, so it does not show real growth.
Some economists went further. Daniel Hamermesh, an emeritus professor at the University of Texas at Austin, told TechTarget that he “would give the finding very little, if any, weight”, arguing that the survey mainly showed that people were willing to take part. Other critics noted that there was no randomly selected comparison group. The study’s lead researcher, Juliet Schor, accepted that a randomised trial would be the gold standard, but argued that employers first have to be persuaded to try the idea at all.
A council tries it: South Cambridgeshire
South Cambridgeshire District Council began a four-day week trial for desk-based staff in January 2023, mainly to tackle recruitment and retention problems. The then Conservative government objected: in October 2023 the levelling up department told councils to end such trials, and in November it issued the council a formal warning.
Because councils publish performance indicators, this trial produced harder data than most private pilots. Independent analysis by the universities of Salford, Bradford and Cambridge, published in July 2025, found:
- 21 of 24 monitored services improved or stayed the same, and six improved by a statistically significant margin, including call answering, benefit processing times and planning decisions.
- Job applications rose by more than 120% and staff leaving fell by more than 40%.
- Spending on staff above budget fell, saving £399,263 a year, mainly because fewer agency workers were needed.
Residents were less convinced. A separate survey by DJS Research found no significant perceived change in nine services and a perceived decline in three, and 45% of respondents said they supported the four-day week. An earlier evaluation reported by Civil Service World also found that 37% of staff were working more than the 80% of hours the scheme expected, usually by two or three hours a week.
The council voted on 17 July 2025 to make the arrangement permanent, becoming the first UK council to do so. Civil Service World reported that the Labour government had allowed the earlier formal warning to lapse after the 2024 election.
The 2025 follow-up pilot and the first control-group study
In July 2025 the 4 Day Week Foundation reported on a smaller pilot of 17 British organisations and almost 1,000 workers, evaluated by researchers at Boston College. Twelve firms tried a four-day week and five a nine-day fortnight. All 17 kept the arrangement afterwards. According to Research Live, 62% of staff said they experienced burnout less often, 41% reported better mental health and 45% said they were more satisfied with life.
The stronger evidence came from a study published in Nature Human Behaviour in 2025 by Wen Fan and Juliet Schor. It pooled 141 organisations and 2,896 employees across six countries, including the UK, and compared them with 285 employees at 12 companies that did not change their hours. Wellbeing improved in the trial firms but not in the comparison group, and people whose hours fell the most saw the biggest gains. The authors acknowledged that the firms were volunteers, mostly small, and based in English-speaking countries.
The case for and against
The strongest case for
Supporters point to a consistent pattern: in almost every published UK trial, most employers chose to keep the shorter week once they had seen their own numbers, which suggests they were not losing money or service quality they cared about. The council data, which is not self-reported by staff, showed services holding up while recruitment and retention improved. And workers want it: in the CIPD’s 2025 survey, a four-day week with no pay cut was the arrangement employees most often said they wanted, at 45%.
The strongest case against
Sceptics argue that the trials tell us about enthusiastic volunteers, not typical employers. Firms that expect to struggle, such as those with shift-based or customer-facing work, are less likely to sign up. Six months may be too short to see whether early gains fade. Many outcomes depend on staff surveys, and staff have an obvious interest in the arrangement continuing. For roles where output is tied to hours, such as care work, cutting time without cutting pay may simply mean hiring more people.
What the evidence does and does not show
Taken together, the UK trials make a reasonable case that a well-planned four-day week can work for office-based organisations that redesign how they work, for example by cutting meetings and automating routine tasks. Wellbeing gains look real, and they also appear in the one large study with a comparison group.
What the evidence cannot yet answer is whether the model scales to the wider economy, whether productivity gains last beyond the first year, and how it would work in sectors where time on the job is the product. Researchers on both sides agree that larger trials, ideally with randomly chosen participants, would settle more of the argument. For now, the four-day week is best understood as a promising option for some employers, not a proven policy for all.
For an international angle, see our report on how Japan has pushed a four-day workweek amid labour shortages.
Frequently asked questions
Is there a legal right to a four-day week in the UK?
No. There is no statutory four-day week. Employees can ask for flexible working, including compressed or reduced hours, but employers decide whether to agree. When the 2025 pilot results were published, ITV reported that the government had no plans to impose a four-day week.
Did workers take a pay cut in the trials?
No. The main UK pilots kept pay at 100% while reducing hours, on the condition that output was maintained.
How many firms kept the four-day week after the 2022 pilot?
Fifty-six of the 61 participating companies said they would continue, and 18 made it permanent, according to the published results.
Is a four-day week the same as compressed hours?
No. Compressed hours fit the same total hours into fewer, longer days. The trials described here cut total hours, usually aiming for about 32 a week, although average hours in the 2022 pilot fell to around 34.
Sources: ITPro, UK’s four-day week trial ends, shows reduced burnout and sick days (21 February 2023); ITPro, World’s biggest four-day working week trial kicks off (6 June 2022); 4dayweek.io, United Kingdom trial summary (accessed October 2026); Constangy, U.K. study on four-day workweek merits scrutiny (28 February 2023); TechTarget, Four-day workweek productivity claims gather criticism (26 September 2022); South Cambridgeshire District Council, Reports showcase four-day week performance (4 July 2025); University of Salford, Council votes to permanently adopt four-day week (17 July 2025); Civil Service World, Public sector’s biggest four-day work week trial a ‘win-win-win’ (9 July 2024); Civil Service World, Council approves plan to make four-day week permanent (July 2025); Research Live, Four-day working week pilot ‘100% success’ (7 July 2025); ITV News, Four-day work week trial hailed a success (3 July 2025); The Register, report on the Nature Human Behaviour four-day week study (22 July 2025); CIPD, Flexible and hybrid working practices (15 July 2025).
