"What is the most they can work in a week?" sounds like a simple question and has more than one correct answer, because the numbers people quote are answering different things. That is why two managers in the same business can hold opposite views and both feel certain.

Line the numbers up and the confusion goes away.

Forty-eight hours, but as an average

The real ceiling in the UK comes from the Working Time Regulations 1998: a worker must not work more than 48 hours a week on average, overtime included. Two words do the heavy lifting.

The first is included: the 48 hours are not 40 plus 8 of overtime on top, they are the total.

The second is average: the comparison is not made on a single week but over a reference period, normally seventeen weeks, which can be extended in certain cases and by workforce agreement.

In practice a 52-hour week is not by itself a breach, provided the reference period contains shorter weeks that pull the average back below 48. Which is also why you cannot eyeball the check: it is a rolling sum.

The opt-out, and what it does not cover

The UK is unusual here: a worker can voluntarily agree in writing to opt out of the 48-hour average. The opt-out has to be genuinely voluntary, it can be withdrawn with notice, and nobody may be penalised for refusing to sign one.

What the opt-out does not do is switch off everything else. Daily rest, weekly rest and breaks all still apply, and for night workers the limits stay in place regardless.

How to calculate the average properly

The method is duller than it sounds: take the reference period, add up every hour actually worked including overtime, divide by the number of weeks.

Two things that trip most people up:

  • annual leave and sick leave do not count as hours worked, but they do not exist to be used as a way of quietly diluting the average either;
  • the sum runs on real hours, not planned ones. If you want a step-by-step method we wrote one in how to calculate worked hours, and there is a worked hours calculator for a single week.

Worth adding that the 48-hour limit never operates alone. It sits alongside the 11 hours of rest between shifts and weekly rest, and in practice those two rule out plenty of weeks that would have sat comfortably under the ceiling on paper.

Outside the UK the numbers move

If you employ people in more than one country, be careful: the 48-hour average comes from the EU working time directive and is broadly common, but the reference period and the standard week are not. Italy sets normal weekly hours at forty and measures the 48-hour average over four months. Spain works to forty hours a week averaged over the year, with a maximum of nine ordinary hours a day, and the 37.5-hour reduction debated in 2025 never came into force. Neither country has anything like the individual opt-out.

This article is practical orientation rather than legal advice: your own contracts and any collective agreement come first.

What to do with it when building the week

The average has one unintuitive operational consequence: heavy weeks have to be paid for with light weeks that are scheduled, not hoped for. If the plan piles up overruns and defers recovery to "when it quietens down", the average degrades quietly for months and then arrives all at once.

Three habits that keep the number honest:

  • watch the rolling total across recent weeks, not just the current one;
  • schedule the recovery at the same moment you authorise the overrun;
  • keep contracted hours and actual hours as two separate numbers instead of collapsing them into one cell.

In Sked Solve the weekly ceiling and each contract's hours are constraints on generation rather than an audit afterwards: weeks that break the average are never proposed. See how it works at Sked Solve.