Turn clocked work time into decimal hours by subtracting unpaid breaks, converting the remaining minutes to a fraction of 60, and adding that fraction to whole hours. A shift from 08:35 to 17:20 with a 45-minute unpaid break is 8 hours 0 minutes, written as 8.00 decimal hours; 8 hours 30 minutes is 8.50, not 8.30.
Worked example with numbers
Take 08:35 to 17:20. The displayed interval is 8 hours 45 minutes, or 525 minutes. Subtract a 45-minute unpaid break to get 480 minutes. Divide 480 by 60 to get 8.00 decimal hours. If the break were 30 minutes, paid time would be 495 minutes: 8 whole hours plus 15 ÷ 60, which is 8.25 decimal hours.
How to make the calculation
Convert every clock time to minutes after midnight before subtracting: 08:35 is 515 minutes and 17:20 is 1,040 minutes. If the end is numerically earlier than the start, add 1,440 minutes for a shift crossing midnight. Subtract only breaks that are actually unpaid under the relevant record. The work-hours calculator performs the basic interval and break subtraction.
Check the units and assumptions
Decimal hours are hours expressed in base 10, whereas a clock uses 60 minutes in each hour. The conversion is decimal hours = whole hours + minutes ÷ 60.
| Clock minutes | Decimal hours |
|---|---|
| 15 minutes | 0.25 hours |
| 30 minutes | 0.50 hours |
| 45 minutes | 0.75 hours |
Common mistakes
Do not divide minutes by 100, which turns 30 minutes into 0.30 instead of 0.50. Do not subtract 12 from a midnight crossing and lose a day. Do not round every daily entry early when a weekly total is required; preserve minutes, add them, then round only under the organisation’s stated rule. A meal period that was interrupted may need a different treatment than a recorded unpaid break.
When this result does not apply
This arithmetic makes a transparent duration, not a decision about pay. Overtime thresholds, paid breaks, on-call time, travel time, rounding rules, and local employment law can alter a payable total. A DST-crossing shift also needs timezone-aware elapsed-time handling rather than simple local-clock subtraction.
Source for the external fact
The U.S. Department of Labor notes that covered employees must receive pay for all hours worked in its hours-worked fact sheet; the source is named here to distinguish recording a duration from applying a payroll rule.
Related calculators
Use the clock-duration tool to check start and end times, the hours converter for a known multi-day duration, and the offset calculator when a recorded time belongs to another zone.