Calculating hours worked takes three steps: find the time between clock-in and clock-out, subtract unpaid breaks, then convert the result to decimal hours for payroll.
Step 1: Find the time between start and end
The easiest way to avoid AM/PM mistakes is to use 24-hour time: add 12 to any PM hour (except 12 PM). 5:15 PM becomes 17:15.
Example: 8:30 AM to 5:15 PM is 8:30 to 17:15.
- Subtract the hours: 17 − 8 = 9 hours.
- Subtract the minutes: 15 − 30 = −15 minutes.
- If the minutes are negative, borrow an hour: 8 hours and 45 minutes.
Overnight shifts: if the end time is earlier than the start time, add 24 hours to the end time. A 10:00 PM to 6:30 AM shift is 22:00 to 30:30, which is 8 hours 30 minutes.
Step 2: Subtract unpaid breaks
Take off any unpaid meal break. 8 hours 45 minutes with a 30-minute unpaid lunch is 8 hours 15 minutes worked.
Under federal rules, short breaks of about 5 to 20 minutes are counted as work time and must be paid. Meal periods of 30 minutes or more can be unpaid if you are fully relieved of duties. Many states have their own break requirements on top of this.
Step 3: Convert minutes to decimal hours
Payroll uses decimal hours, and this is where most mistakes happen. 7 hours 45 minutes is not 7.45 hours. It's 7.75, because 45 minutes is three quarters of an hour.
To convert, divide the minutes by 60:
| Minutes | Decimal hours | Minutes | Decimal hours |
|---|---|---|---|
| 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 |
To convert back, multiply the decimal part by 60: 8.42 hours is 8 hours and 0.42 × 60 ≈ 25 minutes.
A full week's timesheet
| Day | In | Out | Unpaid break | Hours worked | Decimal |
|---|---|---|---|---|---|
| Monday | 8:30 AM | 5:15 PM | 30 min | 8 h 15 min | 8.25 |
| Tuesday | 8:45 AM | 5:00 PM | 30 min | 7 h 45 min | 7.75 |
| Wednesday | 9:00 AM | 6:10 PM | 45 min | 8 h 25 min | 8.42 |
| Thursday | 8:30 AM | 4:50 PM | 30 min | 7 h 50 min | 7.83 |
| Friday | 8:00 AM | 12:40 PM | none | 4 h 40 min | 4.67 |
| Total | 36 h 55 min | 36.92 |
At $22 an hour, this week pays $812.17 before taxes. For the most accurate pay, add up the minutes first (2,215 minutes ÷ 60 = 36.9167 hours) and multiply by the rate once at the end; multiplying the rounded 36.92 gives $812.24, a few cents too much.
Overtime
Under the federal Fair Labor Standards Act, non-exempt employees must be paid at least 1.5 times their regular rate for hours over 40 in a workweek. Overtime is calculated per workweek; you can't average two weeks together.
Example: 46.5 hours in a week at $22 an hour.
- Regular pay: 40 × $22 = $880.00
- Overtime pay: 6.5 × $33 (1.5 × $22) = $214.50
- Total: $1,094.50
A few states have stricter rules. California, for example, also requires overtime for hours over 8 in a single workday, and double time over 12.
Rounding time punches
Federal rules allow employers to round clock times to the nearest 5 minutes, tenth of an hour or quarter hour, as long as the rounding evens out over time and doesn't consistently shortchange employees. Rounding 8:07 to 8:00 and 8:08 to 8:15 is a typical quarter-hour rule.
Let the calculator add it up
The Time Duration Calculator calculates hours between any two times, including overnight shifts, deducts unpaid breaks and totals a whole timesheet in decimal hours. To turn your hours into weekly or yearly pay, use the Hourly to Salary Calculator or see our hourly to salary chart.
Frequently asked questions
How do I convert 7 hours 45 minutes to decimal?
Is 15 minutes 0.15 or 0.25 hours?
Are lunch breaks paid?
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