Time Duration Calculator

Find the exact hours, minutes, and seconds between two times, including overnight shifts. Results update as you type.

Start time
::
End time
::
Duration
9h 00m 00s
9 hours, 0 minutes, and 0 seconds
Decimal hours
9.00
Total minutes
540
Total seconds
32,400

What Is a Time Duration Calculator?

A time duration calculator tells you exactly how much time passes between a starting time and an ending time. Instead of counting on your fingers or converting everything to 24-hour format in your head, you enter both times and instantly get the elapsed hours, minutes, and seconds.

Common uses include:

  • Checking the length of a work shift or meeting
  • Timing a commute, workout, or study session
  • Verifying hours before filling out a timesheet
  • Calculating overnight shift lengths that cross midnight

How It Works

Both times are converted to seconds since midnight, subtracted, and formatted back into hours, minutes, and seconds. If the end time is earlier than the start time, 24 hours are added so overnight ranges like 11 PM to 7 AM come out correctly as 8 hours.

How to Calculate Time Duration by Hand

  1. Convert both times to 24-hour format. Add 12 to PM hours (except 12 PM): 2:45 PM becomes 14:45.
  2. Subtract the start from the end, hours and minutes separately.
  3. Borrow an hour if the minutes go negative: take 1 from the hours and add 60 to the minutes.
  4. Add 24 hours to the end if the period crosses midnight.

Example 1: 9:15 AM to 2:45 PM

14:45 − 9:15 = 5 hours 30 minutes (5.50 hours).

Example 2: 10:40 PM to 6:15 AM (overnight)

The end is on the next day, so 6:15 becomes 30:15. The minutes don't subtract (15 − 40), so borrow: 30:15 becomes 29:75. Then 29:75 − 22:40 = 7 hours 35 minutes (7.58 hours).

Adding Up Several Durations

To total several intervals, such as split shifts or tasks across a day, add the hours and the minutes in separate columns, then carry every 60 minutes into an hour. 2:45 + 3:30 + 1:50 is 6 hours and 125 minutes; 125 minutes is 2 hours 5 minutes, so the total is 8 hours 5 minutes. Converting each interval to decimal hours first (2.75 + 3.50 + 1.83) avoids the carrying entirely.

Duration in Decimal Hours

Timesheets and invoices usually want decimal hours, which the calculator shows under the result. Divide the minutes by 60: 7 hours 35 minutes is 7 + 35 ÷ 60 = 7.58 hours. Looking for a quick answer for a standard shift? See how many hours common shifts are, from 9 to 5 to 12-hour nights.

Frequently Asked Questions

How do I calculate the duration between two times?

Enter a start time and an end time, and the calculator shows the elapsed time in hours, minutes, and seconds, plus the total in minutes and in seconds.

Does it work for overnight shifts?

Yes. If the end time is earlier than the start time, the calculator assumes the end time is on the next day, so a 10 PM to 6 AM shift correctly shows 8 hours.

Can I use the current time?

Yes. Click the "Now" button next to either field to fill in the current time from your device clock.

How many hours is 9:15 AM to 2:45 PM?

5 hours 30 minutes, or 5.5 hours. In 24-hour time that is 14:45 − 9:15 = 5:30.

How do I add up several durations?

Add the hours and the minutes separately, then turn every 60 minutes into an hour. 2:45 + 3:30 + 1:50 is 6 hours 125 minutes, which is 8 hours 5 minutes.

How do I subtract a break from the duration?

Subtract the break from the result: 8 hours 30 minutes with a 30-minute lunch leaves 8 hours. For a full week of shifts with breaks, use the time card calculator, which deducts breaks for you.

How is this different from the time card calculator?

This tool measures a single interval between two times. The time card calculator tracks a whole week of shifts, deducts breaks, and produces a downloadable PDF timesheet.

More Free Time Tools