Time Duration Calculator

Time duration calculator at a glance#

A time duration calculator works out how much time passes between a start time and an end time, in hours and minutes. Subtract the start from the end: if the end minutes are smaller, borrow 60 minutes from the hours. When the end time is on the next day, add 24 hours to it first.

Worked example: from 9:15 AM to 5:45 PM. The hours go from 9 to 17 (5:45 PM in 24-hour time), which is 8 hours, and the minutes go from 15 to 45, which is 30 minutes. That is 8 hours 30 minutes. As decimal hours, 30 minutes is 30 / 60 = 0.5, so the duration is 8.5 hours.

Enter your start and end times in the calculator above for the exact duration, including across midnight or between two dates. Decimal hours are handy for payroll and billing, and the result counts the full span unless you subtract break time yourself.

Durations that cross midnight#

When the end time is earlier on the clock than the start, the shift ran into the next day, so add 24 hours to the end before subtracting. A shift from 10:00 PM to 6:00 AM reads as 22:00 to 6:00; add 24 to the end (6 becomes 30) and 30 - 22 = 8 hours.

The calculator above handles this for you and can also span two full dates, counting every day in between. Borrowing still applies to the minutes: if the end minutes are smaller than the start minutes, take 60 from the hours first.

Turning a duration into decimal hours#

For payroll or billing, convert the minutes part to a decimal by dividing by 60. A duration of 7 hours 45 minutes is 45 / 60 = 0.75, so 7.75 hours. A duration of 6 hours 20 minutes is 20 / 60 = 0.33, so 6.33 hours.

Time duration FAQ#

How do I calculate hours worked from a start and end time?#

Subtract the start time from the end time. For 9:00 AM to 5:30 PM, that is 8 hours 30 minutes. If a break is unpaid, subtract it: take off a 30 minute lunch and you have 8 hours worked.

Can I add or subtract two durations?#

Yes. Add the hours and minutes separately, then carry any minutes over 60 into the hours. 2 hours 50 minutes plus 1 hour 30 minutes is 3 hours 80 minutes, which becomes 4 hours 20 minutes.

How do I read the result in decimal hours?#

Divide the leftover minutes by 60 and add the whole hours. 8 hours 30 minutes is 8 + (30 / 60) = 8.5 hours, the format most payroll and billing systems expect.

Does it work for overnight shifts?#

Yes. When the end time falls on the next day, the calculator adds 24 hours automatically, so 11:30 PM to 7:15 AM returns 7 hours 45 minutes.

Does it deduct breaks?#

The duration is the full span between the two times. Subtract any unpaid break yourself, or use the work hours calculator, which takes a break field and removes it for you.