How hours are calculated
Minutes = end − start (add 24 hours if the end is earlier, for overnight)
Worked = minutes − break
Decimal hours = worked minutes ÷ 60
Worked = minutes − break
Decimal hours = worked minutes ÷ 60
Times are turned into minutes after midnight first. 9:00 AM is 540, and 5:30 PM is 1,050.
Worked example
From 9:00 AM to 5:30 PM with a 30-minute lunch: 1,050 − 540 = 510 minutes. Minus 30 is 480 minutes, which is 8 hours (8.00 decimal).
An overnight shift from 10:00 PM to 6:15 AM: the end is earlier than the start, so add 24 hours. (375 + 1,440) − 1,320 = 495 minutes. With a 45-minute break that's 450 minutes, or 7 hours 30 minutes (7.50).
Minutes to decimal hours
| Minutes | Decimal | Minutes | Decimal |
|---|---|---|---|
| 5 | 0.08 | 35 | 0.58 |
| 10 | 0.17 | 40 | 0.67 |
| 15 | 0.25 | 45 | 0.75 |
| 20 | 0.33 | 50 | 0.83 |
| 25 | 0.42 | 55 | 0.92 |
| 30 | 0.50 | 60 | 1.00 |
Don't type 8:30 as 8.30 on a payroll form: 30 minutes is half an hour, so it's 8.50.
Limitations
- Shifts over 24 hours can't be shown with two clock times. Use the time calculator to add up long durations.
- Daylight saving nights. A shift across the spring or fall clock change is really an hour shorter or longer than the clock times suggest.
- Paid breaks. Under federal rules, short breaks of about 20 minutes or less are paid work time (U.S. Department of Labor). Only enter breaks that are unpaid, typically meal breaks of 30 minutes or more.
Sources
- U.S. Department of Labor Fact Sheet #22: Hours worked (which breaks count as work time)