Enter values and select Calculate to see your result.
Add or subtract two durations in hours, minutes and seconds
Durations can exceed 24 hours. Enter HH:MM:SS; negative results are supported.
How to use the Time Calculator
Add or subtract durations in hours, minutes and seconds, including periods longer than a day.
- Enter the first duration as HH:MM:SS.
- Choose Add or Subtract and enter the second duration.
- Calculate the normalized duration.
Time Calculator formula
Durations convert to seconds, are added or subtracted, then formatted as hours, minutes and seconds.
Worked example
Inputs: 02:30:00 plus 01:45:00.
What to expect: The total duration is 04:15:00.
How to read your result
This is duration arithmetic, not a clock time; values may exceed 24 hours.
Frequently asked questions
Can I enter 30 hours?
Yes. Durations may exceed 24 hours.
What if subtraction is negative?
The result keeps a negative sign to show direction.