How to calculate hours worked
Updated . Checked against U.S. Department of Labor guidance.
To calculate hours worked, subtract your start time from your end time, then take off any unpaid breaks. Do this for each day and add the days together for the week. For payroll, turn the minutes into decimal hours by dividing them by 60. For example, 8:30 AM to 5:00 PM with a 30-minute lunch is 8 hours.
The rest of this guide goes through each step with examples, including night shifts, split shifts, and the mistakes that most often make a timesheet wrong. If you'd rather not do it by hand, the work hours calculator does all of it for a full week.
Step by step
1. Convert the times to 24-hour format
Leave AM times as they are (12 AM becomes 0). Add 12 to PM hours, except 12 PM. 5:30 PM becomes 17:30.
2. Subtract the start time from the end time
Subtract minutes from minutes and hours from hours. If the minutes are negative, add 60 and take 1 from the hours.
3. Take off unpaid breaks
Subtract unpaid meal breaks. Leave short paid rest breaks in.
4. Add up the days in the workweek
Add the hours for each day, carrying every 60 minutes into an hour.
5. Convert to decimal hours
Divide the leftover minutes by 60 and add them to the hours, so payroll can multiply by the hourly rate.
Example: one normal day
You start at 8:45 AM, finish at 5:20 PM and take a 30-minute unpaid lunch.
- End time in 24-hour form
- 17:20
- Start time
- 08:45
- Minutes: 20 − 45 is negative, so 80 − 45
- 35 min
- Hours: 16 − 8 (one hour was borrowed)
- 8 h
- Time at work
- 8:35
- Minus unpaid lunch
- −0:30
- Hours worked
- 8:05 = 8.08 h
Night shifts that cross midnight
When the end time is earlier than the start time, the shift ran past midnight. Add 24 hours to the end time before you subtract. Or split the shift at midnight and add the two parts together.
Example: 10:00 PM to 6:30 AM. In 24-hour form that is 22:00 to 06:30. Add 24 hours to the end: 30:30 − 22:00 = 8:30. So 8 hours 30 minutes, before any unpaid break.
Which day do those hours belong to? For overtime, all that matters is which workweek they fall in, and most payroll systems put the whole shift on the day it started. If a night shift straddles the end of your workweek, ask payroll how they split it.
Which breaks to subtract
Under the federal Fair Labor Standards Act, two kinds of break are treated differently:
- Short rest breaks, usually 20 minutes or less, are hours worked. Don't subtract them.
- Meal periods, typically 30 minutes or more, don't have to be paid if you are completely relieved of duty. These are the breaks you subtract.
If you eat at your workstation while still answering calls or watching a machine, that meal time is generally work time. Some states have their own break rules, and some employers pay for lunch anyway.
Adding up the week
Add the hours, then the minutes, then carry every 60 minutes into an hour. Monday 8:05, Tuesday 7:50, Wednesday 8:20, Thursday 8:00 and Friday 7:45 give 38 hours and 120 minutes. 120 minutes is 2 hours, so the week is 40:00.
Overtime is counted per workweek. A workweek is a fixed, recurring 168-hour period that your employer sets, and it doesn't have to start on Monday. Under federal law, hours over 40 in that week are overtime at one and a half times your regular rate. Two weeks can't be averaged together. California and a few other states also have daily overtime. The overtime calculator works out the pay.
Converting to decimal hours
Payroll multiplies hours by a rate, so it needs decimal hours. Divide the minutes by 60: 8 hours 5 minutes is 8 + 5 ÷ 60 = 8.08 hours. The minutes to decimal chart lists every minute from 1 to 60.
Common mistakes
- Reading 7.30 as seven and a half hours. 7.30 in decimal is 7 hours 18 minutes. Seven and a half is 7.50.
- Mixing up 12 AM and 12 PM. 12 AM is midnight (00:00), and 12 PM is noon (12:00).
- Subtracting paid breaks. Only unpaid meal periods come off.
- Adding minutes as if they were decimals. 7:45 + 7:30 is 15:15, not 14:75 or 15.15.
- Averaging overtime across a pay period. Check each workweek on its own.
- Forgetting rounding. If your time clock rounds punches, your paid hours can differ from your real hours by a few minutes. See how time clock rounding works.
The formula on one line
Hours worked = (end time − start time) − unpaid breaks, with 24 hours added to the end time if it is earlier than the start time. Decimal hours = hours + minutes ÷ 60.