Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Add or subtract two HH:MM:SS durations.
2h 15m 0s
This calculator adds or subtracts two durations expressed as HH:MM:SS -- stopwatch-lap-style math rather than clock-of-day math, so durations can exceed 24 hours (useful for summing video lengths, workout splits, or cumulative task time).
Enter two durations in HH:MM:SS format and choose add or subtract. The result shows the combined (or difference) duration, also in HH:MM:SS.
Each duration is converted to total seconds (hours x 3600 + minutes x 60 + seconds), added or subtracted, then converted back to hours/minutes/seconds. A negative result is shown with a negative sign rather than wrapping around.
1:45:00 + 0:30:00 = 2 hours 15 minutes.
For clock-time-of-day math (a start and end time within a single day) instead of duration math, use the Time Duration Calculator.
The tool takes exactly two durations at a time. To total a list, enter the first two, add them, then type the result in as duration 1 and enter the next item as duration 2. Repeat until the list is finished. Keep the operation set to add for the whole chain unless you deliberately want to remove time. Writing each running total on paper as you go makes it easy to spot a typing error later.
Suppose a hypothetical playlist has three tracks: 0:47:35, 1:12:50, and 0:38:40. Add the first two: seconds 35 plus 50 is 85, which carries one minute and leaves 25 seconds. Minutes 47 plus 12 plus the carried 1 is 60, which carries one hour and leaves 0 minutes. Hours 0 plus 1 plus 1 is 2. The running total is 2:00:25. Now add 0:38:40: seconds 25 plus 40 is 65, leaving 5 with 1 carried; minutes 0 plus 38 plus 1 is 39. The final total is 2:39:05. The tool does this carrying for you.
Subtract is helpful for finding what is left. If a hypothetical video is 2:39:05 long and you have watched 1:15:30, subtracting gives 1:23:35 remaining. If you subtract a bigger duration from a smaller one, the answer is negative, shown with a minus sign on the hours value. That is a useful signal, for example that you are over a time budget by that amount.
Typical uses include adding up lap or split times, finding the total runtime of video or podcast episodes, tallying cooking or study intervals, and summing time logged across tasks. It is a pure duration calculator, so it cannot account for calendar dates or time zones. For that, use the Elapsed Time Calculator.
Yes -- unlike clock-of-day tools, this treats both inputs as pure durations, so hours can go well past 24 (e.g. summing 30 one-hour video clips).
The result is shown as a negative duration, with a minus sign on the hours value.
No -- add durations two at a time, using the running result as the next "duration 1" input for a longer chain.
Add two, then enter the result as duration 1 and the next duration as duration 2, repeating until all are included.
Convert it first. 1.5 hours is 1 hour 30 minutes, so enter 1, 30, 0.
Yes. It is a duration, not a clock time, so totals like 30 hours are shown as they are.
Reference: U.S. Department of Labor