How to calculate hours between two times
- Convert both times to 24-hour format. 8:30 AM becomes 08:30; 5:15 PM becomes 17:15.
- Subtract the start from the end. Subtract minutes first; if the start minutes are larger, borrow 60 minutes from the hours. 17:15 − 08:30 → 16:75 − 08:30 = 8:45.
- Handle midnight. If the end time is earlier than the start, add 24:00 to the end time before subtracting.
- Remove unpaid breaks. 8:45 minus a 30-minute lunch = 8:15.
- Convert to decimal if needed. 15 ÷ 60 = 0.25, so 8:15 = 8.25 hours.
Adding and subtracting durations
When you add up time, remember that minutes roll over at 60, not 100. Adding 4:50 and 3:20 gives 7 hours 70 minutes, which is 8:10. This is why adding times in a regular calculator or spreadsheet often gives wrong answers. The add/subtract tool above accepts hours:minutes, decimal hours and “h/m” notation on separate lines, mixes them correctly and shows the result in all three formats.
Typical uses include totaling hours across several jobs, adding up project or billable time, adding overtime from multiple timesheets, or subtracting time off from a scheduled total.
Common time calculations
| Shift | Break | Hours | Decimal |
|---|---|---|---|
| 9:00 AM – 5:00 PM | 30 min | 7:30 | 7.50 |
| 8:00 AM – 5:00 PM | 60 min | 8:00 | 8.00 |
| 7:00 AM – 3:30 PM | 30 min | 8:00 | 8.00 |
| 8:30 AM – 5:15 PM | 45 min | 8:00 | 8.00 |
| 7:00 AM – 7:00 PM | 30 min | 11:30 | 11.50 |
| 11:00 PM – 7:00 AM | none | 8:00 | 8.00 |
Rounding time for payroll
Many employers round punch times rather than paying to the exact minute. U.S. Department of Labor rules (29 CFR 785.48) allow rounding to the nearest 5 minutes, tenth of an hour (6 minutes) or quarter hour (15 minutes), as long as the practice is neutral over time and does not consistently shortchange employees. With quarter-hour rounding, a punch at 8:07 rounds down to 8:00 and a punch at 8:08 rounds up to 8:15. If your workplace rounds, round each punch first and then enter the rounded times; if it pays to the minute, enter the exact times shown on the clock.
Tracking a full week? The time card calculator totals every day, separates overtime and estimates gross pay. Working with 24-hour schedules? See the military time chart.