Use the free Duration Sum Calculator below: your data never leaves your browser — all work happens on your device, and nothing is uploaded to any server.
Time adds up in awkward ways. A playlist of 01:20:30, 45:10, and 1h 20m does not add like ordinary numbers, because minutes roll over at 60 and hours at 24. Doing it by hand means converting everything to seconds, adding, and converting back, and one slip ruins the total. The Duration Sum Calculator takes a pasted list of durations, one per line, parses each one to seconds, adds them, and shows the total as hours, minutes, and seconds, plus the total in seconds, the count, and the average.
The accepted shapes cover the ways people actually write durations. HH:MM:SS is the full form, MM:SS is the common short form for songs and clips, plain seconds cover raw numbers, and mixes like 1h 20m 30s cover the way people write durations in notes and messages. Each line is parsed on its own, so a list can mix shapes freely: a playlist exported in one shape and a manual note in another still add correctly together.
To use it, paste your durations one per line into the box. The sample mixes all four shapes. Press Add durations. The result shows each line with its parsed value, so you can check that every line was read as you intended, followed by the total in both HH:MM:SS and seconds, the number of durations added, the number skipped, and the average duration. That per-line breakdown is the checking step that makes the total trustworthy.
Ambiguity deserves a plain note. A value like 45:10 is read as 45 minutes and 10 seconds, because that is the standard meaning of two-part durations. If you meant 45 hours and 10 minutes, write it as 45:10:00 instead. A plain number like 90 is read as 90 seconds, not 90 minutes, because raw numbers in time tools are seconds by convention. When a total looks wrong, the per-line breakdown shows which line was read differently from what you expected, and fixing that line fixes the total.
Skipped lines are counted, never guessed. A line like about an hour has no clear numeric value, so it is left out rather than turned into an invented number. A line like 1:2:3:4 has too many parts and is skipped too. If many lines are skipped, the source probably uses a shape the parser does not know, such as durations with words in another language or decimal hours like 1.5h. Converting those to a supported shape first solves it.
Totals above 24 hours are shown as-is, such as 27:15:00, rather than rolling into days, because most duration totals are project hours, playlist lengths, or training time, where 27 hours is clearer than 1 day and 3 hours. If you need days, divide the total seconds by 86400. The average is rounded down to whole seconds, which is honest for planning and avoids pretending to a precision the inputs never had.
People use this calculator to total playlists and video runtimes, to add up work sessions for a timesheet, to sum exercise durations across a week, and to check the length of a course made of many lessons. In each case the job is the same: many small times, one trustworthy total. Because the work happens in the browser, your lists never leave the device, and closing the page clears the paste from view.
How to add durations
- Paste your durations, one per line, in any supported shape.
- Press Add durations.
- Check the per-line breakdown for any line read differently than expected.
- Read the total in HH:MM:SS and in seconds, plus the count and average.
- Fix any skipped lines and run it again if the total looks wrong.
Frequently asked questions
Is 45:10 minutes or hours? Minutes and seconds. For hours and minutes, write three parts, such as 45:10:00.
Is a plain number seconds or minutes? Seconds, by convention. Write 90 as 1:30 if you mean a minute and a half.
Why was a line skipped? It did not match any supported shape. The tool leaves it out rather than guessing a value.
Is my data uploaded? No. Everything runs in your browser, and nothing is sent or stored.
Paste the times, check the breakdown, and trust the total. That is all duration arithmetic needs, and it is all this tool does.
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