Convert tools

Duration Calculator

Add or subtract durations in HH:MM:SS format, including values longer than 24 hours and negative results.

Convert in your browser · No sign-up

Minutes and seconds must be 00–59. This adds durations, not clock times or time zones; hours support up to 12 digits.

Up to 100,000 UTF-16 units per input and 1,000,000 per result. See the supported formats and examples below.

How to use

  1. Add or subtract durations in HH:MM:SS format, including values longer than 24 hours and negative results.
  2. Choose the mode or options, then run the tool.
  3. Review the result, then copy or download the TXT file.

Example

01:30:00 + 00:45:30 = 02:15:30

Details and limitations

Minutes and seconds must be 00–59. This adds durations, not clock times or time zones; hours support up to 12 digits.

Text stays in your browser; it is not sent to a conversion server.

FAQ

Duration Calculator — What are the supported inputs and limits?

Minutes and seconds must be 00–59. This adds durations, not clock times or time zones; hours support up to 12 digits.

Format references

Tool page updated: