Time Duration Calculator

This free online time duration calculator finds the exact time difference between a start time and an end time in hours, minutes, and seconds. Enter both times in 12-hour format and instantly see how long the interval between them lasts, even if it crosses midnight.

How to Use the Time Duration Calculator

  1. Enter the Start Time hour, minute, and (optionally) second, then choose AM or PM.
  2. Enter the End Time hour, minute, and (optionally) second, then choose AM or PM.
  3. Click "Calculate" to see the duration between the two times shown above.
  4. Click "Clear" to reset all fields and start a new calculation.

Frequently Asked Questions

It converts both the start and end times to 24-hour format, then to total seconds since midnight, and subtracts the start time from the end time to get the duration in hours, minutes, and seconds.

Yes. If the end time is earlier than the start time, the calculator automatically adds 24 hours so the duration reflects an overnight span correctly.

No, the Second field is optional for both start and end time. If left blank, it is treated as 0 seconds.

Yes, it's completely free and requires no sign-up.
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