Time Duration Calculator

How to calculate time duration

Convert both clock times to one consistent format, identify any day boundary, subtract the start, and then deduct a valid break.

Step by step

  1. Write start and end in 24-hour time.
  2. If the end is on the next day, add 24 hours to its hour value.
  3. Subtract minutes, borrowing 60 minutes when needed.
  4. Subtract hours, then deduct any break.

Worked example

From 8:35 AM to 4:20 PM, borrow one hour: 15:80 − 8:35 = 7 hours 45 minutes.

Check your answer

Use the time duration calculator for clock intervals, time addition calculator for several durations, or decimal hours calculator for conversion.

Common questions

Should I use 12-hour or 24-hour time?

Either works when written consistently. A 24-hour clock makes day-boundary arithmetic easier.

When should I round?

Keep the exact value unless the task or applicable policy tells you to round.