The 48-hour week on a trades firm: the 17-week average, a 55-hour push worked out, and the 11-hour rest between days

A job runs late, the client wants it finished, and the crew say they are happy to do long days for a fortnight. Before you agree, it helps to know the limit on the working week and how it is measured. GOV.UK's page on maximum weekly working hours says: "You cannot work more than 48 hours a week on average." It adds that the average is "normally averaged over 17 weeks". Both statements come from the page as we read it on 16 October 2026.

That is an average, not a cap on any one week. A 60-hour week is not a breach on its own. A run of them without quieter weeks to balance them is.

What the 17-week average means in hours

Multiply 48 by 17 and you get 816 hours. That is the most a worker can put in over a 17-week stretch without going over the average. Anything above 816 is over the limit, however it is spread.

Here are three crews on the same 17 weeks. The figures are ours, worked from the 48-hour and 17-week numbers above.

Crew A has no room left. One more 55-hour week, in place of a 38, would push the total to 833, which is crew B. That single week is the difference.

How much of a push is left?

The more useful question is how many hours you can still ask for. Take a crew that has worked 14 weeks at 40 hours, which is 560 hours. The three weeks left in that 17-week window can hold 816 minus 560, which is 256 hours. Spread evenly, that is 85.3 hours a week, which is not possible in practice, as a week has 168 hours and the rest rules below apply. The sums show that the average is rarely the real limit on a short push: tiredness, the rest rules and the safety of the people on site come first.

Now take the same crew after 14 weeks at 48 (672 hours). Three weeks can hold 144 hours, which is 48 a week. No room at all for a push.

Steps to run it for your own crew:

1. List each person's hours for the last 17 weeks, including travel time that counts as working time in your contract and any second job you know about.
2. Add them up and subtract from 816.
3. Divide what is left by the weeks remaining. That is the average you can still ask for.
4. Check it against the rest rules below before you promise the client anything.

The rest rules sit alongside it

GOV.UK's page on rest breaks at work says workers "have the right to 11 hours rest between working days". A crew that finishes at 9.30pm cannot be asked to start before 8.30am. Workers also get either "an uninterrupted 24 hours without any work each week" or "an uninterrupted 48 hours without any work each fortnight". Someone working over six hours a day gets "one uninterrupted 20 minute rest break during their working day".

So a long-hours push has three tests, not one: the 17-week average, the 11 hours between days and the weekly or fortnightly rest. A schedule can pass the first and fail the other two. If a night finish means a late start the next morning, plan for it in the programme rather than hoping.

Opting out

The page says workers "can choose to work more by opting out of the 48-hour week". We did not read the separate opt-out page, so we cannot tell you how to word one or what a worker may withdraw. Read that page before relying on it. The opt-out covers the 48-hour average; this guide has not checked whether it also affects the rest rules, so do not assume it does.

The page also lists jobs that can exceed the limit, such as emergency services or security and surveillance. A small trades firm is not on the list as we read it.

Employees, workers and subcontractors

The limit is written for workers. We have not read GOV.UK's guidance on who counts as a worker, employee or self-employed, so we do not say here whether a subcontractor you pay under CIS is covered. If the crew is a mix, check the status of each person.

Keep a record

GOV.UK says "Your employer needs to keep some records about working hours" and sends readers to Acas for the specifics. We did not read the Acas page. A timesheet showing each person's weekly hours and finish times is a sensible start, and it makes the 17-week sum a two-minute job.

Where the cost lands

Long weeks also cost money elsewhere. Our guide to statutory sick pay from day one shows what an absence costs the firm now that pay starts on the first day, and the guide on the apprentice minimum wage is worth a look if apprentices are on your overtime list, since their hours and pay are set by different rules. Our guide to auto-enrolment for a first employee shows how extra pay can change pension contributions.

Overlyft builds AI staff who join the team, and one of them can do this specific task: keep a running 17-week total of each person's hours from the timesheets, flag anyone heading for 816 and list who has had less than 11 hours between shifts, so the owner can plan the next push.

This is not legal or financial advice. Check the source pages on GOV.UK before you act. We did not read the opt-out page, the Acas records guidance or the guidance on worker status, and the figures above are our own sums from the GOV.UK numbers.