What the time calculator does
Adding 1:45:30 to 2:30:45 in your head is harder than it looks because time is base 60, not base 10. This calculator adds or subtracts two durations given as hours, minutes and seconds and returns the result in the same form, plus the total in seconds, minutes and decimal hours. Use it for timesheets, editing and media work, race splits, cooking, and anything else where durations have to be combined.
How it works
Convert each duration to seconds, add or subtract, convert back.
2:30:45 = 2×3600 + 30×60 + 45 = 9,045 s
1:45:30 = 1×3600 + 45×60 + 30 = 6,330 s
Add: 9,045 + 6,330 = 15,375 s = 4 h 16 min 15 s (4:16:15)
Subtract: 9,045 − 6,330 = 2,715 s = 0 h 45 min 15 s (0:45:15)
Decimal hours: 15,375 ÷ 3600 = 4.27 hDoing it by hand: add the seconds; if the sum is 60 or more, carry one minute. Add the minutes; if 60 or more, carry an hour. Subtracting works the same way with borrowing — 30 seconds minus 45 seconds borrows a minute to become 90 − 45 = 45.
Minutes to decimal hours
| Minutes | Decimal hours | Minutes | Decimal hours |
|---|---|---|---|
| 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 |
Payroll and billing systems almost always want decimal hours: 7 hours 45 minutes is 7.75, not 7.45. The calculator's decimal output avoids the classic timesheet error of typing minutes after the point.
Common uses
- Timesheets and invoices — totalling several sessions of work into billable hours.
- Video and audio editing — summing clip durations to hit a target length, or working out how much to cut.
- Sport — combining lap or leg splits into a total, or finding the gap between two finishers.
- Cooking and lab work — chaining timed steps to know when the whole process finishes.
- Travel — adding flight legs and layovers to get total journey time.
- Study and productivity — tallying focused sessions.
Durations vs clock times
This tool works with durations (how long), not clock times (what time). You can still use it for clock arithmetic — 14:30 plus 2:45 is 17:15 — as long as the result stays within one day; a result of 26:10 means 02:10 the next day. For questions like “hours between clock-in and clock-out, minus a break” the Hours Calculator handles the overnight wrap and the break deduction directly. For dates, use the Date Calculator.
Input tips
- Enter durations as
H:MM:SS; hours can exceed 24 and can have more than two digits (130:00:00). - Minutes and seconds above 59 are accepted and normalised:
0:90:00is treated as 1:30:00. - Leading zeros are optional:
1:5:0is 1:05:00. - If a subtraction would go negative, the result is shown as a negative duration, which is the gap in the other direction.