How to find the duration between times
The duration is the end time minus the start time. If the end is earlier than the start, the calculator assumes the period crosses midnight into the next day. For a 9:00 start and 17:30 end, the duration is 8 hours 30 minutes (8.5 hours).
Subtracting clock times is awkward by hand because minutes run in base 60 rather than base 10. The reliable method is to convert both times to minutes past midnight, subtract, then convert back: 17:30 is 1,050 minutes, 09:00 is 540, and 1,050 − 540 = 510 minutes, which is 8 h 30 min or 8.5 decimal hours.
Overnight periods use the same trick with 24 hours added to the end time. A shift from 22:00 to 06:00 becomes 06:00 + 24 h = 30:00, so 1,800 − 1,320 = 480 minutes, exactly 8 hours. This is why an end time earlier than the start is read as the next day rather than as a negative result.
How to use this calculator
Enter a start time and an end time. The result shows the duration in hours and minutes, plus decimal hours — useful for timesheets and shift length. To count to an upcoming time from now, use the hours until calculator.
The output is given both ways because the two audiences differ. A rota or a schedule is read in hours and minutes, while payroll, invoicing and project tracking expect decimal hours — and mixing the notations is the classic error. Eight hours and fifteen minutes is 8.25 hours, never 8.15; a quarter hour is 0.25, a half is 0.5 and three quarters is 0.75.
Two things the calculator deliberately does not do. It does not subtract unpaid breaks, so deduct a 30-minute lunch yourself — a 09:00 to 17:30 day with a half-hour break is 8 paid hours, not 8.5. And it does not account for a daylight saving change, which makes one night 23 hours and another 25. For an overnight-heavy week the hours until calculator counts forward from now, and the days between dates calculator handles spans longer than a day.
Frequently asked questions
- How do I calculate the time between two times?
- Subtract the start time from the end time. This calculator shows the result in hours and minutes and as decimal hours.
- What if the end time is before the start?
- It assumes the period crosses midnight and adds 24 hours, which suits overnight shifts.
- What is 9:00 to 17:30?
- 8 hours 30 minutes, or 8.5 hours.
- How do I get decimal hours for a timesheet?
- Divide the total minutes by 60. The calculator shows this decimal value automatically.
- Does it subtract lunch breaks?
- No — it returns the gross time between the two clock readings, so unpaid breaks have to be deducted separately. A 09:00 to 17:30 shift is 8.5 hours on the clock but 8 paid hours once a 30-minute lunch is removed.