Time Duration Calculator
Add up or subtract lengths of time, such as video clips, workouts or tasks, and convert hours and minutes to decimal hours and back.
How durations are added
Total = sum of (hours × 3600 + minutes × 60 + seconds), shown as h:mm:ss
Each duration is turned into seconds, the seconds are added or subtracted, and the total is turned back into hours, minutes and seconds. Minutes and seconds carry over at 60, not at 100, which is why adding times on an ordinary calculator goes wrong.
Example: 1 h 45 min + 2 h 30 min − 50 min. In minutes that is 105 + 150 − 50 = 205 minutes, which is 3 hours and 25 minutes: 3:25:00, or 3.4167 decimal hours.
You may enter more than 59 minutes or seconds (for example 90 minutes); they are carried over automatically. Totals above 24 hours are not wrapped round to the next day: 26 hours stays 26:00:00, and the result also shows it as 1 day 2 hours.
Decimal hours
Timesheets and invoices often need hours as a decimal number. Divide the minutes by 60 and the seconds by 3600: 7 hours 45 minutes is 7 + 45/60 = 7.75 hours. A frequent mistake is to read 7:30 as 7.30 hours; it is 7.5 hours. To go the other way, multiply the decimal part by 60: 0.2 hours is 12 minutes.
| h:mm | Decimal hours |
|---|---|
| 0:06 | 0.1 |
| 0:12 | 0.2 |
| 0:15 | 0.25 |
| 0:20 | 0.3333 |
| 0:30 | 0.5 |
| 0:45 | 0.75 |
| 1:10 | 1.1667 |
| 7:45 | 7.75 |
Durations versus clock times
This calculator works with lengths of time, not with times of day. To work out how long a shift lasted from its start and end times, including shifts past midnight, use the hours worked calculator. To find a date a number of days away, use the date calculator.
Common questions
Can the result be negative?
Yes. If you subtract more than you add, the result is shown with a minus sign, for example −0:15:00 when a task took 15 minutes less than planned.
How are fractions of a second handled?
You can enter decimals, such as 1.5 hours or 12.25 seconds. The h:mm:ss result is rounded to the nearest second; the decimal-hours result shows up to four decimal places.