How to Calculate the Hours Between Two Times
Finding the hours between two times sounds simple, but it trips people up because a clock runs on base 60, not base 10 — so you can't just subtract the numbers. The reliable method: put both times on a 24-hour clock, subtract the start from the end, and convert the leftover minutes carefully. If you'd rather not think about the base-60 part, the hours calculator works out the hours and minutes between any two times for you.
The base-60 trap
Here's the mistake. From 1:45 to 5:15 looks like "5:15 − 1:45," and if you subtract like decimals you'd get 3.70 or even a negative in the minutes. But minutes only go up to 60, not 100. The real answer is 3 hours and 30 minutes. Treating time like ordinary numbers is where almost every hours error comes from.
How to calculate hours between two times
- Convert both times to a 24-hour clock (so 5:30 PM becomes 17:30).
- Subtract the start time from the end time — hours from hours, minutes from minutes.
- If the minutes go negative, borrow: take one hour (60 minutes) from the hours column.
Worked example. A shift from 9:15 AM to 5:30 PM:
- In 24-hour time: 17:30 − 09:15
- Minutes: 30 − 15 = 15
- Hours: 17 − 9 = 8
- Total: 8 hours and 15 minutes
Overnight shifts
When the end time is earlier than the start — a shift that runs past midnight — add 24 hours to the end before subtracting. A shift from 10:00 PM to 6:00 AM becomes 30:00 − 22:00 = 8 hours. For anyone totting up a week of shifts like this, the time card calculator adds them all and handles the midnight crossovers for you.
Decimal hours for payroll
Payroll doesn't run on "8 hours 15 minutes" — it runs on decimal hours, where 15 minutes is 0.25 of an hour, not 0.15. The conversion is minutes ÷ 60: 15 ÷ 60 = 0.25, so 8:15 is 8.25 hours. Get this wrong and a timesheet is off on every line. The time to decimal calculator converts hours and minutes to decimal, and the minutes to hours converter handles a raw pile of minutes. This post is one of our time and date calculators.
Frequently asked questions
How do I calculate the hours between two times?
Convert both times to a 24-hour clock, subtract the start from the end, and borrow 60 minutes from the hours column if the minutes go negative. The result is the hours and minutes between them.
Why can't I just subtract the times like normal numbers?
Because minutes run 0 to 60, not 0 to 100. Subtracting clock times as if they were decimals gives the wrong minutes — 5:15 minus 1:45 is 3 hours 30 minutes, not 3.70.
How do I calculate hours for an overnight shift?
Add 24 hours to the end time before subtracting. A 10:00 PM to 6:00 AM shift becomes 30:00 − 22:00 = 8 hours.
How do I convert minutes to decimal hours for payroll?
Divide the minutes by 60. So 15 minutes is 0.25 hours, 30 minutes is 0.5, and 45 minutes is 0.75. That makes 8 hours 15 minutes equal to 8.25 hours.
How many hours is a 9-to-5?
From 9:00 AM to 5:00 PM is 8 hours. Subtract an unpaid lunch and the paid total is often 7.5 hours.
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