How to add or subtract time
Enter the hours, minutes, and seconds for each duration. Choose whether to add or subtract the second from the first. The result is shown in hh:mm:ss format along with the total in minutes and total seconds. Seconds and minutes automatically carry over — for example, 1h 45m + 30m = 2h 15m. If the result is negative (subtracting a larger duration), the output is prefixed with a minus sign.
Time unit reference
1 hour = 60 minutes = 3,600 seconds. 1 day = 24 hours = 1,440 minutes = 86,400 seconds. 1 week = 168 hours. Common workout: a 5K run of 28m 30s + warmup 10m = 38m 30s total. Common work: 7h 30m shift + 45m overtime = 8h 15m.
Frequently Asked Questions
What if minutes or seconds exceed 59?
The calculator accepts any non-negative integer for each field. Values above 59 are automatically carried over — for example, entering 90 minutes is treated as 1 hour 30 minutes.
Can I calculate the difference between two clock times?
Yes — treat each clock time as a duration from midnight. For example, to find the time between 9:30 AM and 4:15 PM, enter 9h 30m and 4h 15m and use subtraction (or vice versa). For overnight spans crossing midnight, add 24 hours to the later time first.