Calculate shift pattern hours and pay

A 4-on-4-off pattern with 12-hour shifts averages 42 hours per week. The maths: in an 8-day cycle (4 on, 4 off) you work 4 out of every 8 days, which is 4/8 × 7 = 3.5 days per week. At 12 hours per shift that is 3.5 × 12 = 42 hours per week on average.

A 4-on-4-off 12-hour shift pattern produces 2,184 hours per year (42 hours/week × 52 weeks). Workers on this pattern typically work around 182–183 shifts per year. Note that this is an average — actual hours in any given week will be either 48 hours (4 shifts) or 36 hours (3 shifts) depending on where the cycle falls.

A 3-on-3-off pattern is a 6-day rotating cycle where employees work 3 consecutive shifts followed by 3 consecutive days off. On 12-hour shifts this produces exactly the same average as 4-on-4-off: 3/6 × 7 = 3.5 days per week × 12 hours = 42 hours per week and 2,184 hours per year. The difference is that the cycle is shorter (6 days rather than 8), so the days worked rotate through the week faster.

Yes, in most cases. Under the Working Time Regulations 1998, workers cannot average more than 48 hours per week over a 17-week reference period unless they have signed a written opt-out agreement. Most 12-hour shift patterns (4-on-4-off, 3-on-3-off, 2-on-2-off) average 42 hours per week — which is under 48 hours — so a formal opt-out is not technically required if the average is verified. However, employers should audit the reference period carefully as bank holiday adjustments and overtime can push the average above 48 hours.

A rotating shift pattern is one where employees cycle through different shift times — typically days, afternoons, and nights — on a recurring schedule. This distributes unsocial hours fairly across the team rather than permanently assigning some workers to nights. Common examples include continental shifts (a 4-week cycle of days, afternoons, and nights) and 3-shift rotation systems used in manufacturing and healthcare.

Multiply the average weekly hours by the hourly rate to get weekly gross pay, then multiply by 52 for annual gross pay. For example, a 4-on-4-off worker on 12-hour shifts at £15/hour earns: 42h/week × £15 = £630/week × 52 = £32,760/year gross (before tax and National Insurance). Use the calculator above to check any pattern and rate instantly.

Shift workers on irregular patterns accrue holiday in hours rather than days. Under the Working Time Regulations, workers are entitled to 5.6 weeks of paid holiday per year. For a 4-on-4-off worker averaging 42 hours per week, this is 5.6 × 42 = 235.2 hours of holiday per year. Holiday pay must reflect the average pay over the last 52 weeks, including any regular shift premiums or overtime.

A continental shift pattern is a 4-week rotating schedule typically used in manufacturing and process industries. It covers 24/7 operations by rotating teams through morning shifts, afternoon shifts, and night shifts with rest days in between. A common version runs a 28-day cycle with four teams covering three 8-hour shifts. The pattern balances unsocial hours fairly across all workers.

On a 4-on-4-off pattern, the contracted average is typically 42 hours per week. Any hours worked above the contracted hours — whether due to an extended shift, additional callouts, or covering absent colleagues — may attract overtime pay, depending on the employment contract. Because the pattern produces alternating weeks of 48 hours and 36 hours, overtime thresholds should be assessed over the full cycle rather than week by week. Check the contract to confirm whether overtime is calculated daily, weekly, or per cycle.

A compressed working week is when an employee works their contracted hours across fewer days than the standard five. Common examples include four 10-hour days (4-on-3-off at 8 hours gives 32 hours/week, but a compressed week might be 4 × 10 = 40 hours over 4 days). Unlike a rotating shift pattern, a compressed week typically has consistent start and finish times. Under UK law, employees can make a flexible working request for a compressed week after 26 weeks of employment.