On 4 on 4 off you work half of all days: 181 to 184 twelve-hour shifts in a normal year, 182.5 on average, at an average of 42 hours a week. Every number in this post follows from one fact: the cycle is 8 days long and the week is 7. This is the arithmetic-only companion to our broader 4 on 4 off overview, which covers what the pattern is like to live on.
We make Lumical, an app that scans work rosters into your calendar, so read this with that in mind. Nothing below needs the app. It is all calendar math you can check by hand.
| Question | Answer |
|---|---|
| Cycle length | 8 days: four 12-hour shifts, four off |
| Hours per cycle | 48 |
| Average weekly hours | 42 (no single week contains 42) |
| Shifts per year | 181 to 184, average 182.5 |
| Hours per year | 2,172 to 2,208, average 2,190 |
| Weekends fully off | 3 of every 8 on days, 2 of every 8 on nights |
What does 4 days on 4 days off mean
Four 12-hour shifts in a row, then four full days off, then the same again. The cycle never resets to a weekday. Because 8 does not divide into 7, each work block starts one weekday later than the last: a Monday start becomes a Tuesday start, and after eight cycles (56 days) you are back where you began. That one-day slide is behind every oddity below.
How many days a year do you work on 4 on 4 off
About 182, which is exactly half the year on average. The precise count moves. A 365-day year holds 45 complete cycles (360 days, 180 shifts) plus 5 spare days, and those 5 days carry between 1 and 4 shifts depending on where your rotation sits on January 1. So the honest answer is 181 to 184 shifts, 182.5 on average. In hours: 2,172 to 2,208, averaging 2,190. If your count and your contract disagree by a shift, this remainder is usually why. No year contains a whole number of cycles.
4 on 4 off average weekly hours
42, but no week actually contains 42. Four 12-hour shifts per 8 days is 48 hours per cycle, and 48 scaled to a 7-day week is 42. That is the nominal figure contracts quote. On the ground, any calendar week holds exactly three or four of your shifts, so every week is either 36 or 48 hours. A useful shortcut if your shifts are not 12 hours: the pattern always averages 3.5 shifts a week, so multiply your shift length by 3.5.
Why pay never lines up with the cycle
The 36 and 48 hour weeks do not alternate. They come in runs: four 48-hour weeks in a row, then four 36-hour weeks, repeating every 8 weeks. If you are paid weekly, your payslip swells and shrinks in month-long waves even though your rota never changed.
Monthly pay has its own quirk, because no month is a multiple of 8 days either. A 31-day month always holds 15 or 16 of your shifts. A 28-day February can hold anywhere from 12 to 16, since its 4 spare days can be a whole work block or a whole off block. Whether the heavy weeks count as overtime is a contract question, and rules vary by country and employer, so check yours rather than trusting a blog.
How many weekends does 4 on 4 off give you
On day shifts, three of every eight weekends are completely free. The drift walks your off block through the week, so the free weekends cluster: three in a row with both days off, then five straight weekends where work touches a Saturday or Sunday. On nights it drops to two of every eight, because a Friday night shift ends Saturday morning and spoils a weekend that looks free on paper. The Friday night rule covers that trap in detail.
The count for a specific year depends on where your crew’s rotation falls, so we do not guess it here. The 4 on 4 off calendar for 2026 computes the exact number for your starting position, and the 2027 calendar is ready for when your roster rolls over. If your partner works a different pattern, the free days off together tool shows which off days you actually share.
What the arithmetic cannot tell you
All of this assumes a clean rotation. Real rosters are not clean: a swap, a bank holiday, overtime tacked onto an off day, a training course mid-block. The moment your roster deviates from the pure cycle, the only reliable source is the printed sheet on the break-room wall. That is the part Lumical handles. It scans a photo of the roster, reads every shift including the messy ones, and files them in your calendar on the correct days. You review the result before anything saves.
Working 4 on 4 off from a printed roster? Get Lumical on the App Store and carry the whole cycle in your calendar.