How To Calculate Work Hours (Hours Worked)
To calculate hours worked, take your end time, subtract your start time, then take off any unpaid break. This guide shows each step on a time card, with night shifts, decimals and rounding.
The Four Steps
- Write both times on the 24-hour clock. 8:30 AM stays 8:30, and 5:00 PM becomes 17:00. This stops AM and PM mix-ups.
- Subtract the start from the end. Take hours from hours and minutes from minutes. If the minutes go below zero, borrow 60 minutes from the hours.
- Take off unpaid breaks. Subtract any unpaid lunch. Short paid breaks stay in your hours.
- Add up the days. Add each day's hours and minutes, then turn every 60 minutes into one hour.
Most mistakes come from steps one and two. Reading 5:15 as five and a quarter hours, or forgetting to borrow, shifts the total by a full hour or more.
A Worked Example
You start at 8:45 AM, finish at 5:15 PM and take a 30 minute unpaid lunch. Here is each step with the numbers.
| Step | What you do | Result |
|---|---|---|
| 1. 24-hour | 8:45 AM is 8:45, and 5:15 PM is 17:15 | 8:45 and 17:15 |
| 2. Subtract | 15 minus 45 is below zero, so borrow an hour: 75 minus 45 is 30, and 16 minus 8 is 8 | 8:30 |
| 3. Break | Take off the 30 minute lunch | 8:00 |
| 4. Total | Five days like this | 40:00 |
The same day is worth $160.00 at $20 an hour. Multiply the paid hours by your rate, and read the paid time as a decimal when you do (see below).
Turning Minutes Into Decimal Hours
Payroll systems often want hours as a decimal, such as 7.75 instead of 7:45. Divide the minutes by 60 and add the result to the whole hours.
So 45 minutes is 45 ÷ 60 = 0.75, and 7:45 is 7.75 hours. Add the minutes for the whole week first and convert once, so the total does not drift from rounding every day.
| Minutes | Decimal hours |
|---|---|
| 10 min | 0.17 |
| 15 min | 0.25 |
| 20 min | 0.33 |
| 30 min | 0.50 |
| 45 min | 0.75 |
| 50 min | 0.83 |
Every minute from 1 to 60 is on the decimal hours converter.
Night Shifts That Cross Midnight
If your end time is smaller than your start time, the shift ran past midnight. Add 24 hours to the end time before you subtract.
For 10:00 PM to 6:30 AM, the end becomes 6:30 + 24 = 30:30. Then 30:30 minus 22:00 is 8:30. Most payroll systems count the shift on the day it started.
Take the break off the same way as on a day shift. A 30 minute meal break on that night shift leaves 8:00 of paid time.
To check any two times, use the shift hours calculator.
Adding Up A Full Week
Work out each day the same way, then add the days. In a sample week of five days, the paid time is 8:00, 8:00, 8:00, 8:00, 7:30. The total is 39:30.
Convert once at the end. 39:30 is 39.50 hours, which is $790.00 at $20 an hour before tax.
If the week passes 40 hours in the US, the extra time is usually paid at a higher rate. Overtime is worked out per workweek, not per pay period.
See how the extra pay works in the overtime calculator.
Doing It In Excel Or Google Sheets
Put the start time in column B, the end time in C and unpaid break minutes in D. This formula gives decimal hours and copes with night shifts:
=MOD(C2-B2,1)*24-D2/60Format the result as a number with two decimals. The MOD function wraps a negative result around midnight, which is why it works for a shift that ends the next morning.
The full formulas are in hours worked in Excel.
Rounding Punches
Some employers round each punch to the nearest 5, 6 or 15 minutes. That is allowed only if it evens out over time, so it does not always cut your pay.
With 15 minute rounding, 1 to 7 minutes past the quarter rounds down and 8 to 14 rounds up. A punch at 8:07 counts as 8:00, and 8:08 counts as 8:15.
Employers may round time to the nearest 5 minutes, tenth of an hour or quarter hour, if the rounding averages out over time. Employees must be fully paid for all the time they work. Source: US Dept. of Labor, 29 CFR 785.48. Checked November 2026.
Try your own punches in the time card rounding calculator.
Common Mistakes
- Treating minutes as decimals. 7 h 30 m is 7.50 hours, not 7.30.
- Counting clock hours instead of time passed. 9:00 to 10:00 is one hour, not two.
- Taking off paid breaks. Short rest breaks stay in your hours.
- Rounding every day, then adding. Add the minutes first, then round once.
- Forgetting that a shift can pass midnight. An end time smaller than the start time is not an error.
Rest breaks of 5 to 20 minutes are paid and count as hours worked. Source: US Dept. of Labor, 29 CFR 785.18. Checked November 2026.
Questions People Ask
When counting hours, do you count the first hour?
Yes, but you count time that passes, not the hours on the clock face. From 9:00 to 5:00 is 8:00, even though nine different hours appear.
How do I calculate hours worked in a week?
Work out each day, add the hours and minutes, then turn each 60 minutes into an hour. The sample week above comes to 39:30.
How do I calculate my average hours per week?
Add the hours from several weeks and divide by the number of weeks. Four weeks of 38, 42, 40, 36 hours average 39 hours.
How do I work out my pay from my hours?
Multiply decimal hours by your hourly rate. 37.50 hours at $20 is $750.00 before tax. Overtime may add more.
How do I calculate hours on a time card?
Write each day's clock in and clock out, subtract the unpaid lunch, then add the days. The sample week above comes to 39:30.
How do I calculate hours worked with a lunch break?
Subtract the unpaid lunch from the time between clock in and clock out. A day from 8:45 AM to 5:15 PM with a 30 minute lunch is 8:00.
Sources
- US Dept. of Labor, hours worked fact sheet
- US Dept. of Labor, 29 CFR 785.48
- US Dept. of Labor, 29 CFR 785.18
Written and checked by the countmyworkhours.com team. How we calculate