Time calculator to add or subtract hours, minutes, seconds, and milliseconds, or multiply and divide a duration by a number. Includes live updates, presets, copy result, and compact segmented inputs.
Use this time calculator to add, subtract, multiply, or divide durations without leaving the page. It works well for work shifts, media runtimes, race splits, project timing, and any other duration math that needs hours, minutes, seconds, and milliseconds.
Examples
Add 1 h 45 m and 2 h 30 m to get 4 h 15 m.
Subtract 3 h 20 m minus 1 h 50 m to get 1 h 30 m.
Multiply 02:30:00 by 1.5 to get 03:45:00.
How to add time
Use Add mode for simple duration sums. Enter each time on its own row, then let the calculator carry minutes, seconds, and milliseconds automatically. You can keep precision high with milliseconds on, or hide that field when you only need hours, minutes, and seconds.
For a workday, you might add a shift, a break, and overtime on separate rows. The result updates live as you edit.
How to multiply time
Use Multiply mode when you need to scale a duration by a factor, such as converting one race split into multiple laps or extending media runtime. Use Divide mode to split a total duration evenly across people, tasks, or sessions.
The time input stays compact as HH:MM:SS.MS, so the calculator behaves like a spreadsheet without forcing a wide desktop layout on mobile.
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Time Calculator FAQ
How does the add mode work?
Add mode sums each row as a separate duration. Enter hours, minutes, seconds, and optional milliseconds on each line, then the calculator carries overflow automatically, so 90 minutes becomes 1 h 30 m internally.
How do I multiply or divide time?
Switch to Multiply or Divide, enter one compact time value in HH:MM:SS.MS format, and provide a single number. For example, 02:30:00 × 1.5 gives 03:45:00.
