Duration Calculator
Add or subtract two durations — mix any units — and instantly see the result in plain language and every common unit.
Adding and subtracting time amounts
Sometimes you want to know the total time for two things combined — two flights with a stopover, the runtime of two episodes back to back, or how long a task took across two separate sessions. Enter each duration, pick its unit, and the result appears instantly in plain language.
Duration arithmetic is always exact because every unit is a fixed multiple of a second: 2 hours + 90 minutes is always 3 hours 30 minutes, on any day. This is different from adding time to a specific calendar date, which has to account for varying month lengths and leap years — for that, use the Add / Subtract Time tool instead. Just converting one duration between units? Use the Duration Unit Converter.
Frequently asked questions
How do I add two durations together?
Enter Duration A and Duration B with their units, make sure 'Add' is selected, and the result updates instantly. For example: 2 hours + 90 minutes = 3 hours, 30 minutes.
How do I find the difference between two durations?
Enter the larger duration as A and the smaller as B, then select 'Subtract'. The result shows how much longer A is than B.
Can I mix different units when adding?
Yes — Duration A and Duration B each have their own unit selector. You can add 2 hours + 90 minutes, or 1 day + 360 minutes, and the result accounts for all unit conversions automatically.
What happens when I subtract a larger duration from a smaller one?
The result is shown as a negative duration, prefixed with '−'. For example, 30 minutes − 1 hour = −30 minutes.
How is this different from adding days to a date?
This tool works with pure durations — amounts of time with no anchor date. For adding time to a specific calendar date (e.g. June 1 + 30 days = July 1), use the Add / Subtract Time page.