How to calculate hours worked

Five steps from clock times to payroll hours, with the three mistakes that most often go wrong.

Last reviewed September 23, 2026 by Time Card Calculator Tool

Work it out on your own hours: Hours worked calculator, free with no sign-up.

Adding up hours by hand trips people up because time does not count in tens. Sixty minutes make an hour, twelve hour clocks restart at noon, and night shifts end on a different day from the one they started. The method below works for any shift and gives the same answer as the calculators on this site.

Step 1: convert both times to 24 hour time

Morning times stay the same (9:15 AM is 09:15). For afternoon and evening times, add 12 to the hour (5:30 PM is 17:30). Noon is 12:00 and midnight is 00:00. The military time chart lists every hour.

Step 2: subtract the start from the end

Subtract hours from hours and minutes from minutes. If the end minutes are smaller than the start minutes, borrow an hour: take 1 from the end hour and add 60 to the end minutes.

Step 3: handle shifts that cross midnight

If the end time is earlier than the start time, the shift ran past midnight. Add 24 hours to the end time before subtracting. A shift from 22:00 to 06:30 becomes 30:30 − 22:00 = 8 h 30 min.

Step 4: take away unpaid breaks

Subtract only unpaid meal breaks, usually 30 or 60 minutes. Short rest breaks are paid time and stay in. See are lunch breaks paid for where the line falls.

Step 5: convert minutes to decimal for pay

Divide the minutes by 60 and add them to the hours. 8 h 30 min is 8.5 hours; 8 h 10 min is 8.17 hours. Multiply decimal hours by the hourly rate to get pay. The minutes to decimal chart saves the division.

Adding up a week

Total the days in hours and minutes, then carry every 60 minutes into an extra hour. Five days of 8:20 is 40 hours plus 100 minutes, which is 41 hours 40 minutes, or 41.67 hours. That total is also what the overtime test uses: anything over 40 hours in the workweek is overtime under federal law, so this week has 1.67 overtime hours.

The three most common mistakes

1. Treating minutes as a decimal. Writing 8 h 30 min as 8.30 instead of 8.50 loses 12 minutes a day.
2. Forgetting the AM/PM switch. 8:00 to 4:30 is not −3.5 hours; convert 4:30 PM to 16:30 first.
3. Subtracting paid breaks. A 15 minute rest break is paid; only the unpaid meal comes off.

Let the calculator do it

For one shift, the hours worked calculator takes a start, end and break. For a whole week or pay period, the time card calculator adds every day, applies overtime and shows pay. Both use the same method described here, so you can check one against the other.