How to Calculate Hours Worked (and Convert Minutes to Decimal)
Published 2026-10-27
Adding up a week of start and end times sounds easy until you hit a 7:45 start, a 30-minute lunch and a shift that ends after midnight. Here’s a reliable method, plus the minutes-to-decimal conversion every payroll system needs. The time card calculator does all of it automatically.
Step 1: convert times to 24-hour format
Afternoon and evening times are easier to subtract in 24-hour format: add 12 to any PM hour except 12 PM. So 5:30 PM becomes 17:30, and 9:15 PM becomes 21:15.
Step 2: subtract start from end
For an 8:45 to 17:30 shift: 17:30 − 8:45. Borrow an hour when the minutes don’t work: 17:30 is the same as 16:90, and 16:90 − 8:45 = 8 hours 45 minutes.
Step 3: subtract unpaid breaks
Take off unpaid meal breaks: 8:45 − 0:30 = 8 hours 15 minutes. Under US federal rules, short rest breaks (typically 5 to 20 minutes) count as paid working time, while meal breaks of 30 minutes or more when you’re fully off duty usually don’t.
Overnight shifts
If the end time is earlier than the start, the shift crossed midnight. Add 24 hours to the end time: 22:00 to 6:30 becomes 30:30 − 22:00 = 8 hours 30 minutes.
Step 4: convert minutes to decimal hours
Payroll multiplies hours by a pay rate, so minutes must become fractions of an hour. Divide the minutes by 60: 15 minutes is 0.25 hours, so 8 hours 15 minutes is 8.25 hours, not 8.15.
| Minutes | Decimal | Minutes | Decimal |
|---|---|---|---|
| 5 | 0.08 | 35 | 0.58 |
| 10 | 0.17 | 40 | 0.67 |
| 15 | 0.25 | 45 | 0.75 |
| 20 | 0.33 | 50 | 0.83 |
| 25 | 0.42 | 55 | 0.92 |
| 30 | 0.50 | 60 | 1.00 |
Step 5: total the week and work out overtime
Add the decimal hours for each day. Under the federal Fair Labor Standards Act, non-exempt employees earn at least 1.5 times their regular rate for hours over 40 in a workweek. Some states have stricter rules, including daily overtime. For 44.5 hours at $20 an hour: 40 × $20 = $800, plus 4.5 × $30 = $135, for $935 gross pay.
Common mistakes
- Writing 7:30 as 7.30. Thirty minutes is 0.50 hours, so 7:30 is 7.5.
- Forgetting the overnight rule and getting a negative number.
- Subtracting paid breaks. Only unpaid time comes off.
- Rounding each day differently. Use the same rounding rule every day, or none at all.
To see what an hourly wage adds up to over a year, use the salary to hourly calculator.