How to Calculate Hours Between Two Times

To find the hours between two clock times, convert each to minutes past midnight, subtract, and convert back. The only complication is a shift that crosses midnight.

The Method

For 09:15 to 17:45:

1. Start: 9 × 60 + 15 = 555 minutes 2. End: 17 × 60 + 45 = 1,065 minutes 3. Difference: 1,065 − 555 = 510 minutes 4. Convert: 510 ÷ 60 = 8.5 hours, or 8 hours 30 minutes

Overnight Shifts

If the end time is earlier than the start time, the shift crossed midnight. Add 24 hours (1,440 minutes) to the end before subtracting.

For 22:00 to 06:00:

• Start: 1,320 minutes. End: 360 minutes.
• 360 − 1,320 = −960, which is negative, so add 1,440.
• −960 + 1,440 = 480 minutes = 8 hours

Skipping that step is the single most common error in hand-built timesheets, and it produces a negative or absurd figure rather than a subtly wrong one — which at least makes it easy to spot.

Subtracting Unpaid Breaks

Breaks come out after the span is calculated, not before. A 09:00-17:30 shift with a 45-minute unpaid lunch:

8h 30m − 45m = 7h 45m

Decimal Hours for Payroll

Payroll systems want decimals, not hours and minutes, and the conversion is where money goes missing. 7 hours 45 minutes is 7.75 hours, not 7.45.

Divide minutes by 60. Typing 7.45 instead of 7.75 underpays by 18 minutes a shift, which is over an hour a week.

Daylight Saving Days

Twice a year a day is 23 or 25 hours long. A shift running through the change is an hour shorter or longer in elapsed time than the clock suggests. Most employers pay actual hours worked, which means the clock arithmetic above gives the wrong answer on exactly two days a year. Check your local rule.

Tools

The [time duration calculator](/tools/time-duration-calculator) handles overnight spans and gives the decimal figure directly. For a full week with breaks and overtime, use the [time card calculator](/tools/time-card-calculator).