Calculating work hours sounds trivial until an overnight shift, a split break, or a payroll decimal trips you up. Here is the exact method, with worked examples you can check against the free work hours calculator.
The four-step method
- Step 1 — Find the shift span. Subtract the start time from the end time. 7:30 AM to 4:00 PM is 8 hours 30 minutes.
- Step 2 — Handle overnight shifts. If the end time is earlier than the start time, the shift crossed midnight: add 24 hours. 10:00 PM to 6:00 AM is 8 hours, not negative 16.
- Step 3 — Subtract unpaid breaks. A 30-minute unpaid lunch comes off the total. Paid rest breaks stay in.
- Step 4 — Convert to decimal for pay. Divide leftover minutes by 60. 8 hours 15 minutes becomes 8.25 decimal hours, which payroll multiplies by your rate.
Worked example
Shift: 7:30 AM to 4:00 PM with a 30-minute unpaid lunch, at 22 dollars per hour.
- Span: 8 hours 30 minutes
- Minus unpaid lunch: 8 hours 0 minutes worked
- Decimal: 8.0 hours
- Gross pay: 8.0 x 22 = 176.00
Try the same numbers in the work hours calculator — it also splits regular and overtime hours if you set a threshold.
Overnight example
Shift: 10:00 PM to 6:30 AM with one 45-minute unpaid break.
- Span across midnight: 8 hours 30 minutes
- Minus break: 7 hours 45 minutes worked
- Decimal: 7.75 hours
Where people go wrong
- Forgetting which breaks are unpaid. Only unpaid breaks reduce hours worked — check your employment agreement.
- Rounding minutes casually. 7:47 to 4:02 is 8 hours 15 minutes, not 8 hours. Small daily rounding compounds into real money across a pay period.
- Mixing h:mm and decimal. 8 hours 30 minutes is 8.5 decimal hours, never 8.30.
If you are doing this every shift, that is exactly the job ShiftFlow automates — it logs each shift, applies your break and overtime rules, and shows estimated pay as you go. The calculator is the manual version; the app is the automatic one.