Totaling up a list of video clip lengths, billable time entries, or workout segments by hand is tedious and error-prone once you’re mixing hours, minutes, and seconds. This tool sums (or subtracts) as many HH:MM:SS durations as you want and gives you the total in every format you actually need.
What Is the Duration Calculator?
Enter a list of durations — one per line, in HH:MM:SS, MM:SS, or plain seconds — with an optional leading minus sign to subtract a line, and get the running total instantly as HH:MM:SS, total seconds, and decimal hours (handy for timesheets and billing).
How to Use It
- Open the tool at /tools/duration-calculator.
- Enter each duration on its own line.
- Prefix any line with
-to subtract it from the total. - Read the total in HH:MM:SS, seconds, and decimal hours.
Key Features
- Flexible input formats: HH:MM:SS, MM:SS, or bare seconds, all in the same list.
- Subtraction support, so you can net out breaks or unbillable time directly in the same list.
- Decimal hours output, ready to multiply by an hourly rate for invoicing.
- Per-line breakdown, with invalid lines clearly flagged rather than silently ignored.
When to Use This Tool
- Totaling video or podcast clip lengths to check against a runtime limit.
- Adding up time-tracking entries for freelance invoicing or timesheets.
- Summing interval training or workout segment durations.
Try It Now
Open Duration Calculator directly, or press ⌘K and type the tool name from anywhere on the site.
Part of the Date & Time collection on WebdevToolbox — free, browser-based developer tools with no login required.