📅 Date & Time
How to Calculate the Hours Between Two Times
Work out the hours and minutes between a start and end time — including overnight shifts and unpaid breaks — by hand or with a calculator.
Updated 28 September 2026 · 2 min read
Adding up hours from a timesheet looks simple until the minutes get in the way. The trap is that time isn't decimal — there are 60 minutes in an hour, not 100 — so you can't just subtract the numbers as if they were ordinary decimals.
The reliable method: convert to minutes
The cleanest way to find the gap between two times is to turn each into a plain number of minutes, subtract, then convert back:
- Turn the start time into minutes since midnight: hours × 60 + minutes. So 9:15 is 9 × 60 + 15 = 555.
- Do the same for the end time. 17:45 is 17 × 60 + 45 = 1,065.
- Subtract: 1,065 − 555 = 510 minutes.
- Convert back: 510 ÷ 60 = 8.5, so 8 hours 30 minutes.
The time duration calculator does all of this for you and shows the answer both ways — as hours and minutes, and as a decimal like 8.5 — which is exactly the format most payroll systems want.
Handling shifts that cross midnight
A night shift from 22:00 to 06:00 breaks naive subtraction, because 6 minus 22 is negative. The fix is to recognise the end time falls on the next day and add a full day — 24 hours, or 1,440 minutes — to it before subtracting:
The calculator assumes exactly this: if the end is earlier than the start, it treats it as the following day, so overnight shifts total correctly without any manual adjustment.
Subtracting an unpaid break
For paid hours you usually want to knock off an unpaid lunch. Work out the gross duration first, then subtract the break in minutes:
- A 9:00–17:30 day is 8 hours 30 minutes gross.
- Take off a 30-minute unpaid break and you're left with 8 hours paid.
- Convert to decimal for payroll: 8 hours exactly, or 8.0.
The tool has an optional break field that does this final subtraction automatically.
Decimal hours for pay
Wages are calculated in decimal hours, and this is where minutes trip people up: 8 hours 30 minutes is 8.5 hours, not 8.30. Divide the minutes by 60 to convert — 15 minutes is 0.25, 20 minutes is 0.33, 45 minutes is 0.75. Multiply the decimal hours by the hourly rate to get pay.
If you're tallying whole days rather than hours within a day, our guides to counting working days between two dates and the date difference calculator cover that end of the problem.
Frequently asked questions
- How do I convert minutes to decimal hours?
- Divide the minutes by 60. So 15 minutes is 0.25 hours, 30 minutes is 0.5, and 45 minutes is 0.75. This is what payroll uses, and it's why 8 hours 30 minutes is written as 8.5, not 8.30.
- How do I total an overnight shift?
- When the end time is earlier than the start, add 24 hours to the end before subtracting. A 22:00-to-06:00 shift becomes 30:00 − 22:00 = 8 hours. The time duration calculator does this automatically when the end is earlier than the start.