How to Calculate Hours Worked (with Lunch, Overnight & Decimal Examples)

Every paycheck for hourly work starts with the same arithmetic: when you started, when you stopped, and what came off for breaks. It's easy to get wrong by a few minutes a day — which over a year is real money. Here's the method payroll uses.

1. Write each shift in 24-hour time

Afternoon times are where most mistakes happen. Add 12 to any PM hour from 1 to 11: 5:30 PM becomes 17:30, 11:15 PM becomes 23:15. 12 PM stays 12:00 and 12 AM becomes 0:00.

2. Subtract start from end

17:30 − 9:00 = 8 hours 30 minutes. If the minutes don't subtract cleanly, borrow an hour: 16:10 − 8:45 → 15:70 − 8:45 = 7 h 25 min.

3. Take off unpaid breaks

A meal period of 30 minutes or more, where you're fully relieved of duty, is usually unpaid. Short breaks of 5 to 20 minutes are work time under federal rules and stay in your hours. So 8:00 AM–4:30 PM with a 30-minute lunch is 8 hours, not 8.5.

4. Overnight shifts: add 24 hours

If the shift ends after midnight, the end time is smaller than the start. Add 24 to the end: 22:00 to 6:30 → (6:30 + 24:00) − 22:00 = 8 h 30 min.

5. Add up the week and convert to decimal

Payroll systems want decimal hours. Divide the minutes by 60: 15 min = .25, 30 = .50, 45 = .75, 20 = .33, 40 = .67. A week of 8:30, 8:00, 9:15, 8:00 and 7:45 is 41 h 30 min = 41.50 hours.

6. Find the overtime

Under the federal Fair Labor Standards Act, non-exempt employees get 1.5× their regular rate for hours over 40 in a workweek — here 1.5 hours. A few states, notably California, also count overtime by the day. See how time and a half works.

Common mistakes

• Mixing 7:45 (seven forty-five) with 7.45 hours (seven hours 27 minutes).
• Averaging two weeks: overtime is per workweek, even on a biweekly paycheck.
• Deducting short coffee breaks — under 20 minutes they're paid time.
• Forgetting the overnight correction, which produces negative hours.