Online Tool Store
Time Duration Calculator
Add and subtract a list of durations in HH:MM or HH:MM:SS format and get a running total instantly. Runs entirely in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Example shown — replace with your own durations.
Total
0:00:00
How it works
- Enter one duration per line, in HH:MM or HH:MM:SS.
- Prefix any line with "-" to subtract it instead of adding it.
- The running total updates on every keystroke, shown as HH:MM:SS, minutes, and hours.
The formula
Each line converts to total seconds, then they're summed:
seconds = hours × 3600 + minutes × 60 + seconds
Example: 2:30 + 1:45 − 0:15 = 9,000 + 6,300 − 900 = 14,400 seconds, or 4:00:00.
FAQ
Can I subtract time as well as add it?
Yes — prefix a line with "-" to subtract it from the running total, or "+" (or nothing) to add it.
What formats are accepted?
HH:MM or HH:MM:SS, with hours unrestricted (e.g. "12:45" or "130:00" for very long totals).
Can the total go negative?
Yes — if your subtractions outweigh your additions, the total shows a leading minus sign.
Is my data uploaded anywhere?
No — every calculation happens in your browser as you type.
How we compare
| Feature | Online Tool Store | Spreadsheet time math | Manual addition |
|---|---|---|---|
| No formula syntax to remember | ✓ | ✗ | ✓ |
| Handles carrying past 60 minutes automatically | ✓ | ✓ | ✗ |
| No spreadsheet to open first | ✓ | ✗ | ✓ |
Spreadsheets can do this too, once you remember the right time-format cell settings. Time Duration Calculator gets the same carry-the-minutes math instantly, with nothing to set up.