Duration Calculator — Add and Subtract
Sum work or playback durations without wrapping at midnight
Runs in your browser · nothing is uploaded
What it does
Combine elapsed durations such as work sessions or media running times. Unlike a clock-time calculation, this tool treats every entry as a duration, so totals continue past 24 hours. Negative durations can represent deductions. No calendar dates, time zones or daylight-saving rules are involved.
How to use
- Enter one duration per line as hours:minutes or hours:minutes:seconds.
- Use two digits for minutes and seconds, for example 01:30 or 2:05:09.
- Choose Add all durations, or First minus remaining, then calculate. An optional leading minus sign is supported.
Calculation rules and limits
- Hours can have one to six digits. Minutes and seconds must be between 00 and 59.
- At most 1,000 durations are accepted. An empty line inside the list is an input error.
- Subtraction means the first duration minus every later duration. Subtracting a negative duration adds it.
- Results include a signed duration, total seconds, total minutes and decimal hours. Decimal display uses up to 12 significant digits.
Example
23:30 plus 02:45:30 gives 26:15:30, or 94,530 seconds. 01:00 minus 02:30 gives -1:30:00. The entry 01:30 is 1 hour 30 minutes, not 1.3 hours.
Calculations run in your browser without uploading your calculation data. Changing an input clears the previous result; choose Calculate again to get the updated answer.
FAQ
Does a total reset at 24 hours?
No. A total of 26 hours stays 26 hours because it is elapsed time, not a time of day.
Can it calculate across daylight-saving changes?
No. This tool performs arithmetic on durations only. It does not interpret calendar timestamps or time zones.
What does subtraction do with three rows?
It subtracts both the second and third durations from the first. For example, 5:00, 1:00 and 0:30 produce 3:30:00.
