How to Calculate Hours Worked (With Lunch and Night Shifts)
Last updated · By the DropFlick team
Working out hours by hand is easy once you convert everything to one unit. Here is a method that always works, including for lunch breaks, split shifts and shifts that run past midnight.
The 4-step method
- Write both times in 24-hour format. 8:45 AM stays 08:45; 5:15 PM becomes 17:15.
- Subtract start from end. Subtract minutes first; if you can't, borrow 60 minutes from the hours. 17:15 − 08:45 → 16:75 − 08:45 = 8:30.
- Subtract unpaid breaks. 8:30 − 0:30 lunch = 8:00.
- Convert to decimal if payroll needs it. Divide the minutes by 60: 8:00 = 8.00 hours; 7:45 = 7.75 hours.
Or skip the arithmetic and use the hours calculator, which does exactly these steps.
Example 1: a standard day with lunch
| Step | Calculation | Result |
|---|---|---|
| Clock in / out | 7:50 AM → 4:20 PM | 07:50 → 16:20 |
| Time on the clock | 16:20 − 07:50 | 8:30 |
| Unpaid lunch | 8:30 − 0:45 | 7:45 |
| Decimal hours | 7 + 45 ÷ 60 | 7.75 |
Example 2: a shift that crosses midnight
When the end time is earlier than the start time, add 24 hours to the end time before subtracting. A 10:00 PM to 6:30 AM shift: 06:30 + 24:00 = 30:30; 30:30 − 22:00 = 8:30. Minus a 30-minute unpaid break, that's 8:00 hours worked.
Example 3: a split shift
Work out each part separately and add them. 6:00–10:00 (4:00) plus 15:00–19:15 (4:15) = 8:15, or 8.25 decimal hours. The time between the two parts is not counted.
Adding up a whole week
Add the hours and the minutes in separate columns, then convert every 60 minutes into an hour. For example, five days of 7:45 is 35 hours + 225 minutes = 35 hours + 3 hours 45 minutes = 38:45 (38.75 decimal). Converting each day to decimal first and adding the decimals gives the same answer and is easier on a normal calculator. The time card calculator does the whole week for you, including overtime.
Common mistakes
- Treating minutes as decimals. 7:45 is not 7.45 hours. It's 7.75.
- Deducting paid breaks. Short paid rest breaks are usually working time, so only deduct unpaid breaks.
- Mixing AM and PM. 12:30 AM is just after midnight; 12:30 PM is just after noon.
- Forgetting the overnight rule. A negative result means the shift crossed midnight: add 24 hours.