Shift Schedule Calculator
Lay out a rotating shift pattern such as 4 on 4 off or Panama 2-2-3 on an eight-week calendar, with the average weekly hours.
Averaged over a full cycle this pattern works out to 42 hours per week.
| Week | Sun | Mon | Tue | Wed | Thu | Fri | Sat |
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Updated Formula covered by automated tests
Choose a rotation, the first day of the cycle and your shift length, and the tool lays out which days are on and off for up to eight weeks in a Sunday-to-Saturday grid. It also works out the average number of hours per week the rotation adds up to over a full cycle.
Rotating schedules keep hospitals, police and fire departments, factories, data centers and utilities staffed around the clock. The hard part for the people working them is answering simple questions far ahead: am I on for Thanksgiving, which weekends are free next month, can I take a class that meets every Tuesday? Because each pattern repeats on a fixed cycle that rarely lines up with the 7-day week, those answers shift from week to week.
The formula
- L
- Cycle length in days (8 for 4 on, 4 off; 14 for the Panama 2-2-3)
- i
- Position of the date within the cycle, from 0 to L − 1; the extra + L keeps dates before the start positive
- pattern[i]
- The cycle written as a list of 1s (working) and 0s (off), for example 1,1,1,1,0,0,0,0
- h
- Length of one shift in hours
A rotation is a repeating sequence, so the status of any date is decided by its distance from a known day 1 of the cycle, divided by the cycle length: the remainder says where in the sequence that date sits. This is modular arithmetic, the same idea as a clock face, and it works for dates years ahead as long as the rotation is not interrupted.
Average hours depend only on the share of days worked. The Panama 2-2-3 (two on, two off, three on, two off, two on, three off) and the 4-on-4-off both work half of all days, so with 12-hour shifts both average 42 hours per week, but the hours inside any one calendar week vary: 36 or 48 on a 4-on-4-off, and 60 or 24 on a Panama cycle started on a Monday, which matters for weekly overtime rules.
Worked example
Marcus, an ICU nurse, works 12-hour shifts on a 4-on-4-off rotation whose current cycle began on Monday, November 2, 2026. He wants to know whether he works on December 25.
- 1 Days from the cycle start: November 2 to December 25 is 28 + 25 = 53 days.
- 2 Position in the 8-day cycle: 53 mod 8 = 5 (53 = 6 × 8 + 5).
- 3 Positions 0 to 3 are work days and 4 to 7 are off, so position 5 is the second of his four days off.
- 4 His next shift starts at position 0, three days later on Monday, December 28.
- 5 Average hours: 4 ÷ 8 × 7 × 12 = 42 hours per week.
Result: Marcus is off on Christmas Day 2026 and returns on December 28. Over time his rotation averages 42 hours a week.
Before you rely on the result
- The grid assumes the rotation never breaks. Shift swaps, leave, and day-to-night transitions inside a pattern are not tracked.
- Day and night crews on the same pattern are not distinguished; a night shift that ends the next morning is shown on the day it starts.
Frequently asked questions
What date should I enter as the start?
Enter the first day of a block of work, the day you return after time off. If you enter an off day, the grid will shift so that day is treated as the first on-shift day and every later date will be wrong.
Why do I get overtime some weeks but not others?
Under the US Fair Labor Standards Act, overtime for non-exempt employees is generally based on hours over 40 in a fixed 7-day workweek, not on the cycle average. With 12-hour shifts a 4-on-4-off rotation puts three shifts (36 hours) in some workweeks and four (48 hours) in others. Some hospitals use an 8-and-80 arrangement instead; ask payroll which applies.
Which rotation gives the most full weekends off?
The Panama 2-2-3 is built so that every other weekend is fully off (Friday through Sunday) when the cycle starts on a Monday. A 4-on-4-off drifts through the week, so a given weekend is off roughly half the time and full weekends come in irregular runs.
Does rotating shift work affect health?
Research summarized by NIOSH links long and irregular hours with sleep loss, fatigue and higher injury risk. Forward-rotating schedules and enough rest between blocks help, and anyone with ongoing sleep problems should talk to a clinician.
Sources
- CDC NIOSH: Fatigue and Work (cdc.gov)
- U.S. Department of Labor: Overtime Pay (dol.gov)