Time Duration Calculator (Add and Subtract Time)

How long did it take?

Time between two clock readings sounds simple until the minutes do not line up, or the end time is after midnight. From 08:45 to 17:10 is not 9 hours 35 minutes, and from 22:30 to 06:15 is not negative. This time duration calculator takes two times, or two dates with times, and tells you exactly how much time passed.

The answer comes in hours and minutes, in decimal hours for timesheets and invoices, and in total minutes. Use it for shifts, journeys, how long a job took, or the gap between two events across several days.

Using the calculator

1. Choose Between two times for anything inside a day or overnight, or Between two dates and times for longer spans.
2. Enter the start time and the end time. Your device shows a 24 hour or an AM and PM picker; both work.
3. For dates, set the start date and time and the end date and time.
4. Read the duration, then the same figure in h:mm, decimal hours and minutes.

The elapsed time formula

duration = end time − start time
if the end time is earlier than the start, add 24 hours
with dates: (end date − start date) × 1,440 + end time − start time, in minutes

The calculator turns each clock time into minutes after midnight, subtracts, and turns the result back into hours and minutes. 08:45 is 525 minutes after midnight and 17:10 is 1,030, so the gap is 505 minutes. For two dates, each whole day adds 1,440 minutes.

Worked example: 08:45 to 17:10

• 08:45 is 525 minutes after midnight
• 17:10 is 1,030 minutes after midnight
• 1,030 − 525 = 505 minutes
• 505 minutes = 8 hours 25 minutes

The time between them is 8 hours 25 minutes, which is 505 minutes or 8.42 hours in decimal. If you are filling in a timesheet that wants decimals, 8.42 is the figure to use, not 8.25.

An overnight example: 22:30 to 06:15. The end is earlier than the start, so it is the next morning: 375 + 1,440 − 1,350 = 465 minutes, which is 7 hours 45 minutes.

Doing it by hand

The borrowing method works well on paper. Subtract the minutes first. If the end minutes are smaller, borrow an hour: add 60 to the end minutes and take 1 from the end hours.

Easy ways to get it wrong

• Subtracting clock times like ordinary numbers. 17.10 minus 8.45 is 8.65, which is meaningless as a time.
• Forgetting a lunch break. This page measures the whole span. To take breaks off and total a week, use the time card calculator.
• Mixing AM and PM. 7:30 to 4:15 is 8 hours 45 minutes if the second time is in the afternoon, and almost 21 hours if both are in the morning.
• Ignoring clock changes. On the night clocks go forward or back, real elapsed time is an hour shorter or longer than the clocks suggest. This calculator uses plain clock time.

Frequently asked questions

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