Shift hours calculator
Updated October 8, 2026 · 2 min read · free calculator
Enter how many shifts you work a month, how long they are and how many are nights. The calculator shows hours a month, a week and a year, and the share of your hours between 23:00 and 07:00.
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- Hours a month
- 126 h
- Hours a week
- 29.1 h
- Hours a year
- 1,512 h
- Night hours
- 19%
A week is 12/52 of a month (about 4.33 weeks a month). Night hours assume each night shift covers up to 8 hours between 23:00 and 07:00.
If you count shifts a week, convert first: multiply by 52 and divide by 12. Three shifts a week is 13 shifts a month.
How it calculates
- Hours a month: shifts a month × hours a shift.
- Hours a week: hours a month × 12 ÷ 52, since a month averages about 4.33 weeks.
- Hours a year: hours a month × 12.
- Night hours: up to 8 hours of each night shift, as a share of all hours.
The starting values, 14 shifts of 9 hours with 3 nights, give 126 hours a month, 29.1 a week, 1,512 a year and 19% night hours. The IRS uses the same 52 ÷ 12 ratio when it treats 130 hours a month as the equivalent of 30 hours a week. The step-by-step guide has more worked examples, including 28-day blocks.
Why 23:00 to 07:00
Definitions of night differ. The EU Working Time Directive defines night time as a period of at least 7 hours, set by each country's law, that always includes midnight to 05:00. The calculator uses 23:00 to 07:00, an 8-hour window that includes it.
| Night shift | Length | Night hours |
|---|---|---|
| 23:00 to 07:00 | 8 h | 8 h |
| 21:00 to 07:00 | 10 h | 8 h |
| 19:00 to 07:00 | 12 h | 8 h |
| 22:00 to 06:00 | 8 h | 7 h |
A night that misses part of the window, like 22:00 to 06:00, has fewer night hours than the calculator assumes, so its share comes out slightly high.
From your real schedule
My hours uses your actual shifts instead of averages: bring in a calendar link or .ics file from any scheduling app to see hours per week, nights, quick returns and a 24-hour clock of the hours you worked.
Common questions
- Can I use it for a 28-day block?
- Not directly, since it treats your number as a calendar month. For a block, divide the block's hours by 4 to get hours a week.
- What counts as a night shift here?
- Any shift you enter as a night. The calculator counts up to 8 of its hours, the part between 23:00 and 07:00.
- Why isn't hours a week just hours a month divided by 4?
- A month averages about 4.33 weeks. Dividing by 4 overstates weekly hours by about 8%.
See your own shifts this way.
Bring in your schedule from any scheduling app with its calendar link. Capillary charts your hours, nights, quick returns and hardest shifts. Only you can see it.