How to use Duration Calculator
- Choose the Input notation: HH:MM:SS, MM:SS or decimal hours.
- Type the First duration.
- Choose the Operation: Add, Subtract second duration or Convert first duration only.
- Type the Second duration when the operation needs it.
- The total in every unit updates as you change the durations.
Example: Duration Calculator
Add two recording lengths in HH:MM:SS mode.
Options
- Input notation
- HH:MM:SS, MM:SS and decimal hours are separate modes so 01:50 is never guessed to mean one hour fifty minutes. Pick the notation you actually have.
- Operation
- Add joins two durations, Subtract removes the second from the first, and Convert reports a single duration in every unit.
- Second duration
- Only needed for Add or Subtract. The first duration cannot carry a minus sign, and a subtraction that goes below zero produces a negative total.
Supported inputs and limits
Where your input is processed
This tool processes your input in this browser. Your text and files are not uploaded to UseFreeTools. Check this tool's limits for anything it may save on your device.
Why a duration does not wrap at 24 hours
A clock face repeats every day, so 23:00 plus two hours reads as 01:00 on a 24-hour dial. A duration has no dial, so the same sum keeps counting to 25:00:00. That matters for podcasts, audiobooks, playlists and training totals, where the listener expects one growing figure instead of a time of day.
Questions about Duration Calculator
Why does the total show 24 hours instead of rolling to the next day?
The input is elapsed time, not a clock reading. 23:50:00 plus 00:25:00 is 24:15:00, and the tool keeps the full length instead of wrapping past midnight.
Is 01:50 one hour fifty minutes or one minute fifty seconds?
It depends on the mode. In HH:MM:SS the tool reads 01:50:00 as one hour and fifty minutes. In MM:SS it reads 01:50 as one minute and fifty seconds, which is why the notation is chosen before you type.
How do decimal hours work?
1.5 decimal hours converts to 01:30:00, and 2.25 becomes 02:15:00. Up to three decimal places are accepted.
Can the result be negative?
Yes, in Subtract mode. 02:00:00 minus 00:25:00 is 01:35:00, and a smaller first duration gives a negative total such as -00:10:00.
Does the tool show totals beyond HH:MM:SS?
Every result lists the total in HH:MM:SS, seconds, minutes and hours, plus the exact millisecond value, so you can copy the unit you need.