Time Duration Calculator

Calculate a time difference, add time to a base clock time, or subtract a time interval. The form uses separate fields for hours, minutes, and seconds, so it is precise enough for schedules, workouts, media timing, work logs, and short technical intervals.

How to use this calculator

Choose Time Difference, Add Time, or Subtract Time. For a difference, enter the start and end hour, minute, and second. For addition or subtraction, enter the base time plus the interval in days, hours, minutes, and seconds. The calculator returns a clock-style result and totals in hours, minutes, or seconds.

For work schedules with breaks, use the shift calculator or time card calculator. For dates and birthdays, the age calculator handles calendar months and years.

How it works

The calculator converts each time to seconds after midnight.

$difference\ seconds = end\ seconds - start\ seconds$

If the difference is negative, it adds 24 hours so the interval crosses midnight. Add and subtract mode applies the interval, then wraps the answer within a 24-hour clock.

Worked example

From 13:30:00 to 17:45:00, the difference is 4 hours, 15 minutes, and 0 seconds. That is 4.25 total hours, 255 total minutes, or 15,300 seconds.

Common mistakes

Do not type decimal hours into the minute fields. Enter 1 hour 30 minutes as hour 1 and minute 30. For travel or remote meetings, convert zones first with the time zone calculator, because daylight saving changes can affect real elapsed time.