Time Duration Calculator

Enter a start and an end time as hours, minutes and seconds with AM or PM. The calculator returns the duration in hours, minutes and seconds and also as a single total in decimal hours, in minutes and in seconds. If the end time is earlier than the start, it is assumed to be on the following day. For spans that cross several days, use Time Between Two Dates, which adds full calendar days to the clock difference.

All calculations use plain clock time. When a period crosses a daylight saving change, the real elapsed time is an hour more or less than the clock difference, so adjust for that by hand.

Calculate the duration between two times

To find a duration by hand, first convert both times to the 24-hour clock: add 12 to PM hours from 1 to 11, and treat 12 AM as hour 0. Then subtract the start from the end, working from the seconds up. If the seconds or minutes of the end time are smaller, borrow 60 from the next column, just as you would borrow 10 in ordinary subtraction. If the end hour is still smaller than the start hour, the period crosses midnight, so add 24 hours.

For example, from 8:30:00 AM to 5:30:00 PM: 5:30 PM is 17:30:00, and 17:30:00 − 8:30:00 = 9:00:00, so the duration is 9 hours. From 9:47:15 AM to 2:15:40 PM: convert to 14:15:40, subtract the seconds (40 − 15 = 25), then the minutes, borrowing an hour because 15 is less than 47 (75 − 47 = 28), and finally the hours (13 − 9 = 4), for 4 hours 28 minutes 25 seconds.

To express the result in a single unit, use the conversions below. 4 hours 28 minutes 25 seconds is 4 × 3,600 + 28 × 60 + 25 = 16,105 seconds, or 268.42 minutes, or 4.4736 hours.

Durations matter for timesheets, race and workout splits, flight and travel planning, cooking and billing by the hour. For payroll, decimal hours are the most useful form; for sports and lab timing, seconds are usually clearer.

Frequently asked questions