48-Hour Average Working Week Calculator (UK and EU)
How is the 48-hour average working week calculated?
Add up the hours worked over the reference period (normally 17 weeks), add the hours worked in the days immediately after the period, one for each day lost to annual leave, sickness or family leave, and divide by the number of weeks. In the UK regulations that is (A + B) / C. Leave is put back this way so that a holiday does not pull the average down. Single weeks can exceed 48 hours; the average cannot, unless the worker has signed an opt-out (UK).
A week of holiday counted as zero hours would make a 55-hour habit look like a 52-hour one. The regulations prevent that by replacing leave days with the days worked after the period ends, which is the step most spreadsheets skip.
Enter the weekly hours and any leave days; the calculator gives the average, the week-by-week trend, and how many hours are left before the period goes over.
Built by Muhammad Shahzeb Anwar, MSc Industrial and Organizational Psychology. Long hours are a fatigue and safety question before they are a legal one; the limit exists because performance and error rates change with them.
Your average
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The rule in the UK and the EU
Regulation 4 of the Working Time Regulations 1998 limits working time to an average of 48 hours a week over a reference period of 17 weeks, unless the worker has agreed in writing to opt out. The period is 26 weeks for workers covered by the special-case exceptions (for example where continuity of service or security is needed, or there is a foreseeable surge of activity), and can be extended to up to 52 weeks by a collective or workforce agreement. In the EU, Article 6 of the Working Time Directive sets the same 48-hour average and Article 16 allows a reference period of up to four months; the individual opt-out in Article 22 is optional, and most member states do not use it.
Why leave is added back
Regulation 4(6) gives the formula (A + B) / C. A is the hours worked in the reference period. B is the hours worked immediately after the period in the same number of working days as were "excluded days": days of annual leave, sick leave, maternity, paternity, adoption or parental leave, and days covered by an opt-out. C is the number of weeks. Without B, every holiday would dilute the average and let the rest of the period run longer.
What this will not tell you
This averages the hours you enter. It does not decide what counts as working time (on-call at the workplace usually does; on-call at home depends on how restricted the person is), and it does not check rest breaks, daily and weekly rest, night work or young workers' limits, which have their own rules. Some sectors (road transport, aviation, doctors in training) have their own regimes. Nothing you type leaves your browser.
Questions people actually ask
Can I work more than 48 hours in one week?
Yes. The limit is an average over the reference period, normally 17 weeks, so individual weeks can go over 48 as long as the average does not, unless you have opted out (UK).
Do holidays count as zero hours in the 48-hour average?
No. Days of annual leave, sickness and family leave are excluded, and the same number of working days immediately after the reference period are added instead, so leave does not reduce the average.
Can an employer make me sign the 48-hour opt-out?
No. In Great Britain the opt-out must be voluntary and in writing, the worker must not be treated badly for refusing, and they can cancel it with seven days' notice, or up to three months if the agreement says so.
What is the reference period for the 48-hour week?
17 weeks as standard; 26 weeks for special-case workers; up to 52 weeks under a collective or workforce agreement. In the EU the Directive allows up to four months, longer by collective agreement.
Does the 48-hour limit apply in the EU without an opt-out?
Yes. The Working Time Directive sets a 48-hour average including overtime; the individual opt-out is optional for member states, and most do not allow it.
Sources
Checked against the text of the law on 16 October 2026. Laws and notified rates change; if a source below has moved on, the source wins over this page.
- Working Time Regulations 1998, regulation 4 (48-hour average and the formula): https://www.legislation.gov.uk/uksi/1998/1833/regulation/4
- Working Time Regulations 1998, regulation 5 (opt-out agreements): https://www.legislation.gov.uk/uksi/1998/1833/regulation/5
- Working Time Directive 2003/88/EC, Articles 6, 16 and 22: https://eur-lex.europa.eu/eli/dir/2003/88/oj
- GOV.UK, maximum weekly working hours: https://www.gov.uk/maximum-weekly-working-hours
Cite this tool
Free to use and free to quote. If a figure here is useful in something you are writing, a link back is all that is asked.
Muhammad Shahzeb Anwar, MSc Industrial and Organizational Psychology. 48-Hour Week Average Calculator. Shahzeb Speaks. https://www.shahzebspeaks.com/working-time-48-hour-average-calculator/
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