United Kingdom. Working Time Regulations 1998 limits applied
Shift pattern generator: build the cycle, then test it against the law
Rota software will happily build you a pattern that breaks the Working Time Regulations, because it is optimising for cover and not for compliance. The arithmetic that decides whether a pattern is lawful is small enough to do here: days on, days off, shift length. Out come the cycle length, the average week the pattern actually produces, the crews needed to cover it around the clock, and whether the 48 hour average and the 11 hour daily rest survive contact with it.
48 hours
the average weekly working limit, normally averaged over 17 weeks
11 hours
rest between working days, which a 12 hour shift leaves exactly 12 hours for and a 14 hour shift does not
8 hours
the average night workers must not exceed in a 24 hour period, and a hard ceiling where the work involves special hazards or heavy strain
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What this is based on
- The 48 hour average weekly limit is applied as gov.uk states it: "you cannot work more than 48 hours a week on average, normally averaged over 17 weeks". A worker may choose to opt out of the 48 hour week in writing, and several categories of work sit outside the limit entirely, including jobs requiring 24 hour staffing, the armed forces and emergency services, and roles where working time is not measured and the worker controls their own decisions (gov.uk).
- Average weekly hours are computed from the SHAPE of the cycle rather than from a calendar: days on divided by cycle length, times seven, times the shift length. That is exact for a repeating cycle and is why a 4 on 4 off 12 hour pattern produces 42 hours a week rather than the 48 people assume from the shift length.
- Daily rest is 11 hours between working days and the weekly rest is either an uninterrupted 24 hours each week or an uninterrupted 48 hours each fortnight. Workers also have the right to one uninterrupted 20 minute rest break during the working day where they work more than 6 hours (gov.uk).
- The daily rest figure assumes shifts on consecutive days start at the same clock time, so the gap is 24 hours minus the shift. A pattern that rotates forward from nights to days inside a cycle can produce a shorter gap than this figure shows, and that transition is the one to check by hand.
- Night workers are staff who regularly work at least 3 hours during the night period, which is 11pm to 6am unless the worker and employer agree a different period. They "must not work more than an average of 8 hours in a 24-hour period", usually calculated over 17 weeks, or up to 52 weeks by agreement. Where the work involves special hazards or heavy physical or mental strain the limit is absolute: they "cannot work longer than 8 hours in any 24-hour period" (gov.uk).
- The crew count is arithmetic, not a rota: shifts needed a day multiplied by the cycle length over the days on. It tells you how many crews the pattern implies for the cover you asked for. It does not account for holiday, sickness, training or the relief factor, all of which push the real headcount above it.
- Under 18s are not modelled. gov.uk states that under 18s "cannot work more than 8 hours a day or 40 hours a week", that 16 and 17 year olds "cannot work between midnight and 4am", and that they usually cannot work between 10pm and 6am, with narrow industry exceptions. Any pattern involving young workers needs checking against those rules directly.
- No figure here is a market rate, a typical pay rate or a benchmark. Everything the tool returns is derived from the pattern you enter and the published statutory limits, and nothing is estimated.
Shift Pattern Generator is an independent site operated by Ellul Solutions Ltd. It is not affiliated with, endorsed by or connected to gov.uk, Acas, the Health and Safety Executive or any government body, and it is not a law firm or an employment adviser. Nothing here is legal advice on a particular rota. The tool applies published statutory limits to the pattern you enter and reports where it sits against them; whether a specific pattern is lawful also depends on individual opt-outs, exempt categories, collective or workforce agreements and the sector rules for drivers, seafarers and young workers, none of which it models. We publish no figure that is not either derived from your own inputs or taken from a source cited on this page.
Common UK shift patterns: cycle, average week and Working Time Regulations position, 2026
Last updated
The average week a shift pattern produces is rarely the number people carry in their heads, and it is the number the 48 hour limit is measured against. This table works the arithmetic for the patterns most often used in UK manufacturing, care, security and logistics.
Average weekly hours are days on divided by cycle length, times seven, times the shift length. That is exact for any repeating cycle. Crews are shifts needed a day for continuous 24 hour cover multiplied by cycle length over days on, rounded up to a whole crew, and they exclude any relief factor for holiday, sickness and training. The Working Time position column applies three published limits and no interpretation: the 48 hour average week normally averaged over 17 weeks, the 11 hour daily rest between working days, and the 8 hour average in a 24 hour period for night workers. Where a pattern is over a limit the table says which limit and by how much, rather than saying the pattern is unlawful, because an individual opt-out, an exempt category or a collective or workforce agreement modifying the reference period can each make an over-limit pattern lawful. Every figure is reproducible from the two inputs in the first column and the calculator above runs the same arithmetic, so the tool and the table cannot disagree.
| Pattern | Cycle | Average week | Crews for 24 hour cover | Working Time position on these figures |
|---|---|---|---|---|
| 4 on 4 off, 12 hour shifts | 8 days | 42 hours | 4 | Inside the 48 hour average. Night average is 6 hours in 24, inside the night limit. 12 hour gap clears the 11 hour daily rest by an hour. |
| 3 on 3 off, 12 hour shifts | 6 days | 42 hours | 4 | Identical average to 4 on 4 off, because the ratio is the same. The shorter cycle rotates through the calendar week faster, which changes weekend incidence, not compliance. |
| 5 on 2 off, 8 hour shifts | 7 days | 40 hours | 5 | Inside every limit. Needs five crews for continuous cover because 8 hour shifts mean three shifts a day. |
| 6 on 4 off, 12 hour shifts | 10 days | 50.4 hours | 4 | Over the 48 hour average by 2.4 hours a week. Lawful only with individual opt-outs, an exempt category, or a longer reference period agreed under a collective or workforce agreement. |
| 7 on 7 off, 12 hour shifts | 14 days | 42 hours | 4 | Inside the 48 hour average. The seven consecutive nights need checking against the weekly rest rule: 24 uninterrupted hours a week, or 48 uninterrupted hours a fortnight. |
| 2 on 2 off 3 on, 12 hour shifts | 14 days | 42 hours | 4 | Inside the 48 hour average. Cycle is a fortnight, so it fixes the weekend rotation the shorter cycles keep moving. |
| 4 on 4 off, 12 hour shifts, hazardous night work | 8 days | 42 hours | 4 | Inside the 48 hour average but 4 hours over the absolute 8 hour ceiling that applies where night work involves special hazards or heavy physical or mental strain. That ceiling does not average out. |
- A 4 on 4 off pattern on 12 hour shifts averages 42 hours a week, not 48: the cycle works 4 days in every 8, which is 3.5 shifts a week.
- A 6 on 4 off pattern on 12 hour shifts averages 50.4 hours a week, which is over the 48 hour average limit before any overtime is added.
- Continuous 24 hour cover on 12 hour shifts needs four crews on any 1:1 on-off ratio, and five crews on 8 hour shifts with a 5 on 2 off pattern.
- The 11 hour daily rest right means a shift longer than 13 hours cannot be worked on consecutive days at the same start time without breaching it.
- Night workers must not work more than an average of 8 hours in a 24 hour period, but where the work involves special hazards or heavy physical or mental strain the 8 hours is an absolute ceiling with no averaging.
- The 48 hour week is an average normally taken over 17 weeks, so a pattern can exceed 48 hours in a given week and still comply.
Cite this page
“Common UK shift patterns: cycle, average week and Working Time Regulations position, 2026”, Shift Pattern Generator, https://shiftpatterngenerator.co.uk/ (updated 2026-08-15). Average weekly hours are days on divided by cycle length, times seven, times the shift length. That is exact for any repeating cycle. Crews are shifts needed a day for continuous 24 hour cover multiplied by cycle length over days on, rounded up to a whole crew, and they exclude any relief factor for holiday, sickness and training. The Working Time position column applies three published limits and no interpretation: the 48 hour average week normally averaged over 17 weeks, the 11 hour daily rest between working days, and the 8 hour average in a 24 hour period for night workers. Where a pattern is over a limit the table says which limit and by how much, rather than saying the pattern is unlawful, because an individual opt-out, an exempt category or a collective or workforce agreement modifying the reference period can each make an over-limit pattern lawful. Every figure is reproducible from the two inputs in the first column and the calculator above runs the same arithmetic, so the tool and the table cannot disagree.
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Tell us the shape of the operation and what the current pattern is failing at. Rota and workforce management suppliers who handle that shift shape will contact you directly.
Related guides
Each one cites where its numbers come from.
Common questions
How many hours a week is a 4 on 4 off shift pattern?
42 hours a week on 12 hour shifts. The cycle works 4 days in every 8, which is half the days, so the average is 0.5 times 7 times 12. The intuition that 12 hour shifts must run close to the 48 hour limit is wrong by six hours. The same ratio produces the same answer at any cycle length: 3 on 3 off and 7 on 7 off both average 42 hours on 12 hour shifts, because all three work half the days.
How many crews does a 24 hour operation need?
Four on 12 hour shifts with any equal on-off ratio, and five on a 5 on 2 off pattern with 8 hour shifts. The arithmetic is shifts needed a day, which is cover hours divided by shift length, multiplied by the cycle length divided by the days on. That is the minimum implied by the pattern and excludes any relief factor: holiday, sickness, training and turnover all push the real headcount above it, which is why operations typically staff a continuous rota above the bare four.
Is a 6 on 4 off shift pattern legal in the UK?
On 12 hour shifts it averages 50.4 hours a week, which is over the 48 hour average limit. That does not make it automatically unlawful, but it does mean something else has to carry it: individual written opt-outs from the 48 hour week, an exempt category such as work requiring 24 hour staffing, or a longer reference period agreed under a collective or workforce agreement. Without one of those, the pattern breaches the limit on its own arithmetic.
How much rest is required between shifts in the UK?
11 uninterrupted hours between working days. On consecutive shifts starting at the same time the gap is 24 hours minus the shift length, so 12 hour shifts leave 12 hours and comply, while 14 hour shifts leave 10 and do not. The rule is most often breached during a forward rotation, where a late finish is followed by an early start the next day: both shifts look normal on the rota and the gap between them is under 11 hours.
What are the limits on night shifts in the UK?
Night workers, meaning staff who regularly work at least 3 hours during the night period of 11pm to 6am unless a different period is agreed, must not work more than an average of 8 hours in a 24 hour period. That average is usually taken over 17 weeks, or up to 52 weeks if the workers and employer agree. Where the work involves special hazards or heavy physical or mental strain there is no averaging at all: 8 hours is an absolute ceiling in any 24 hour period.
Does the 48 hour limit apply to every week?
No. It is an average, normally taken over 17 weeks, so a single week above 48 hours does not breach it provided the average across the reference period stays inside. This is why seasonal operations can lawfully run heavy peaks. It also means an employer relying on the averaging has to measure it: assuming the shoulder weeks will bring the average down is not the same as knowing they did.
Does a shift pattern change how much annual leave staff get?
It changes how the entitlement is expressed, not how much there is. Statutory leave is 5.6 weeks a year, and for shift workers a week means a week of that worker's normal hours, which is why leave for a 12 hour shift pattern is usually tracked in hours rather than days. Converting 5.6 weeks of a 42 hour average to days at 8 hours produces a misleading number; converting it at the real shift length does not.
Sources
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