How to Calculate Hours Worked: Overnight Shifts, Rounding and Overtime
Subtract, take off breaks, add 24 hours for overnight shifts; then convert minutes properly (7:45 is 7.75 hours), round only the way federal rules allow, and count overtime per workweek.
Hours in One Shift
Subtract the start time from the end time, then take off unpaid breaks. 9:00 to 17:30 is 8 hours 30 minutes; with a 30-minute unpaid lunch it is 8 hours. A shift that ends after midnight needs 24 hours added: 22:00 to 6:30 is 8 hours 30 minutes. Our Hours Calculator handles both and reads 24-hour or AM/PM times.
Minutes to Decimal Hours
Payroll systems usually want decimal hours, and the classic mistake is writing 7 hours 45 minutes as 7.45. Divide the minutes by 60 instead:
| Minutes | Decimal hours |
|---|---|
| 5 | 0.08 |
| 6 | 0.10 |
| 10 | 0.17 |
| 15 | 0.25 |
| 20 | 0.33 |
| 30 | 0.50 |
| 40 | 0.67 |
| 45 | 0.75 |
| 50 | 0.83 |
So 7:45 is 7.75 hours, and writing 7.45 would underpay 18 minutes.
Rounding Punches
Many workplaces round clock punches. The Department of Labor accepts rounding to the nearest five minutes, tenth of an hour (six minutes) or quarter hour under 29 CFR 785.48(b), as long as it does not, over time, fail to pay employees for all the time they actually worked. With quarter-hour rounding, a punch 1 to 7 minutes past the quarter rounds down and 8 to 14 minutes rounds up. In the calculator’s sample week, five shifts punched 8:58 to 17:07 with a 30-minute lunch come to 38 hours 15 minutes unrounded and 37 hours 30 minutes with quarter-hour rounding; rounding that always favors the employer is what the regulation rules out.
Overtime Over 40 Hours
Under the federal Fair Labor Standards Act, covered non-exempt employees must be paid at least one and one-half times their regular rate for hours over 40 in a workweek, according to the Department of Labor’s Fact Sheet #23. The workweek is a fixed period of seven consecutive 24-hour days, and hours cannot be averaged across weeks: 45 hours one week and 35 the next means 5 overtime hours, not zero. Example: 41.5 hours at $20 an hour is 40 × $20 + 1.5 × $30 = $845 gross. Some states add daily overtime or other rules, and exempt employees are not covered, so check your state.
Calculate your hours
Shift hours, weekly time card, rounding, overtime and decimal hours.
Frequently Asked Questions
How do I calculate hours worked?
How do I convert 7 hours 45 minutes to decimal?
Is rounding time clock punches legal?
When do I get overtime?
Published Oct 14, 2026 by Derek Giordano
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