How to Calculate Hours Worked (Time Card Math)
3 min read
Adding up a timesheet by hand is where mistakes (and lost pay) creep in — especially converting minutes to decimals and subtracting breaks. The math isn't hard once you see it.
Here is how to calculate hours worked from clock times.
Step by step
- 1Convert times to a 24-hour clock
Turn 9:00 AM into 9:00 and 5:30 PM into 17:30 so you can subtract cleanly.
- 2Subtract start from end
17:30 - 9:00 = 8 hours 30 minutes. If a shift crosses midnight, add 24 hours to the end time first.
- 3Subtract breaks
Take off unpaid breaks: 8h30m minus a 30-minute lunch = 8 hours 0 minutes worked.
- 4Convert minutes to decimal for pay
Divide minutes by 60: 30 minutes = 0.5 hours. So 8h30m = 8.5 hours. Multiply by your hourly rate for gross pay. The Hours Calculator does all of this, including breaks and overnight shifts.
Tips
- For payroll, always convert to decimal hours (minutes / 60) — 8 hours 15 minutes is 8.25, not 8.15.
- Decide up front whether breaks are paid or unpaid; it changes the total.
- For shifts past midnight, add 24 hours to the clock-out time before subtracting.
Frequently asked questions
How do I calculate hours worked?
Convert clock-in and clock-out to 24-hour time, subtract start from end, subtract unpaid breaks, then convert any leftover minutes to decimal (minutes / 60) for pay.
How do I convert minutes to decimal hours?
Divide the minutes by 60. 15 minutes = 0.25, 30 = 0.5, 45 = 0.75. So 7 hours 45 minutes is 7.75 hours.
How do I handle a shift that crosses midnight?
Add 24 hours to the clock-out time before subtracting. An 11 PM to 7 AM shift is 31:00 - 23:00 = 8 hours.