How the duration is calculated
Each time is converted to minutes since midnight, the start is subtracted from the end, and any unpaid break is removed:
minutes = ( end − start ) − break
hours = minutes ÷ 60
If the end time is earlier than the start (an overnight span, like 22:00 to 06:00), 24 hours are added so the result is still positive.
Worked example
From 9:00 to 17:30 with a 30-minute break:
End − start: 17:30 − 9:00 = 8 hours 30 minutes (510 minutes).
Minus break: 510 − 30 = 480 minutes.
Duration: 480 ÷ 60 = 8 hours 0 minutes = 8.00 decimal hours.
Hours-and-minutes vs decimal hours
People read time as hours and minutes, but payroll and spreadsheets use decimal hours, where the minutes are expressed as a fraction of 60. So 8 hours 30 minutes is 8.5, and 7 hours 15 minutes is 7.25. This calculator shows both formats so you can use whichever you need.
Tip: for a full weekly timesheet with overtime over 40 hours and gross pay, use the Time Card Calculator instead.