Three 12-hour shifts, then three days off, repeating on a six-day cycle. Enter your hourly rate below to get average weekly hours, annual hours and gross pay — plus a check against the 48-hour Working Time Regulations limit.
Cycle length
6 days
Average week
42 hours
Annual hours
2,190
The pattern runs on a six-day cycle rather than a seven-day week, which is what makes it awkward to administer. Because six does not divide evenly into seven, your shifts land on different weekdays each cycle. A worker on days will start a run on a Monday, then the following run begins on a Sunday, then a Saturday, and so on. It takes six full cycles — 42 days — before the pattern returns to its starting weekday.
Over that 42-day span a worker completes 21 shifts of 12 hours, which is 252 hours in six weeks, or an average of 42 hours per week. Across a full year the same maths gives roughly 2,190 hours, against about 1,825 hours for a standard 35-hour office week.
The 48-hour limit. At a 42-hour average the pattern sits under the weekly limit, so no opt-out is needed for the base rota. Add regular overtime or a handover period and you can cross 48 quickly — six extra hours a week is the entire margin.
Night workers. Where the pattern includes nights, normal hours for night workers should not exceed an average of 8 hours in any 24. A 12-hour night shift breaches that average unless it is offset across the reference period, and night workers are entitled to a free health assessment.
Daily rest. Workers need 11 consecutive hours off between shifts. With 12-hour shifts that leaves exactly 12 hours, so any overrun at the end of a shift eats directly into a statutory entitlement.
Booking leave in days does not work cleanly on this pattern. A worker taking a week off might give up three shifts or four depending on where the week falls in the cycle — so counting in days quietly advantages some staff and penalises others.
The fix is to track entitlement in hours. Statutory leave is 5.6 weeks, so a 42-hour average week gives 235.2 hours of paid leave per year. Deduct the actual shift length when someone books, and everyone gets the same deal regardless of which shifts they drop. Our pro rata holiday calculator handles the same maths for part-time and mid-year starters.
Three-on-three-off is common wherever cover is needed every day but headcount is tighter than a four-team rota allows — ambulance and control room staff, smaller manufacturing lines, care settings, and security contracts covering a single site. Two teams can cover a 24/7 operation on days and nights, where 4-on-4-off generally needs four.
The trade-off is recovery time. Three consecutive 12-hour shifts is a shorter run than four, but the days off never fall on a fixed weekend, which staff often find harder to plan around than the hours themselves.
TimeTally builds 3-on-3-off rotas, tracks hours against the 48-hour limit and deducts leave in hours so the cycle never distorts anyone's entitlement.
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