How to Calculate Hours Worked, With Lunch Breaks

Here is the method payroll people use, with examples you can check against the time card calculator.

1. Convert times to 24-hour format

Add 12 to PM hours (except 12 PM). 5:12 PM becomes 17:12. 12:30 AM becomes 0:30.

2. Subtract start from end

8:47 to 17:12: 17:12 − 8:47. Borrow an hour when minutes go negative: 16:72 − 8:47 = 8:25.

3. Subtract unpaid breaks

8:25 − 0:30 lunch = 7:55. Only subtract bona fide meal periods, ordinarily 30 minutes or more, fully relieved of duty. Rest breaks of 5 to 20 minutes are hours worked (29 CFR 785.18, 29 CFR 785.19).

4. Convert to decimal

Divide minutes by 60: 55 ÷ 60 = 0.92, so 7:55 = 7.92 hours. See the decimal conversion guide.

Overnight shifts

If the shift ends the next day, add 24 hours to the end time. 10:00 PM to 6:30 AM: 30:30 − 22:00 = 8:30, minus a 30-minute meal = 8:00.

5. Add the week and check overtime

Add each day's hours. Under federal law, hours over 40 in the workweek are overtime at 1.5× (U.S. DOL Fact Sheet #23). California also has daily overtime; see the California calculator.

Last reviewed November 2026. This is general information, not legal advice.