Time Duration Calculator

Find the duration between two times, or add and subtract hours and minutes.

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How it works

In duration mode, enter a start and end time and the tool returns the gap as hours and minutes, as a decimal number of hours, and as total minutes. If the end is earlier than the start it can treat it as crossing midnight, and you can add dates for spans longer than a day. In add/subtract mode it shifts a starting time by a duration you enter. The date math uses the well-tested date-fns library and runs entirely in your browser.


              17:30 − 09:15 = 8h 15m = 8.25 hours

Common use cases

  • Totaling hours worked on a shift, including overnight ones.
  • Figuring how long an event or process lasted between two clock times.
  • Adding a 90-minute duration to a start time to find the end.

Frequently asked questions

Can it handle times that cross midnight?

Yes. If the end time is earlier than the start, you can treat the span as crossing midnight so an 11pm-to-2am shift correctly reports three hours rather than a negative value.

Does it give decimal hours for timesheets?

Yes. Alongside the hours-and-minutes breakdown it shows the duration as decimal hours (for example 8h 15m as 8.25), which is what most payroll and timesheet systems expect.

Can I calculate across multiple days?

Yes. Add start and end dates and the duration spans the full interval, counting every hour between the two date-times.