How to Calculate Hours Worked, Step by Step
How to calculate hours worked: subtraction and minutes methods, deducting lunch, overnight shifts like 10 PM to 6 AM, weekly totals, and errors to avoid.
To calculate hours worked, subtract the start time from the end time, take off any unpaid break, and convert the result to decimal hours. For an 8:30 AM to 5:00 PM day with a 30-minute unpaid lunch, that is 8 hours 30 minutes minus 30 minutes, or 8.00 hours. The rest of this page walks through each step, including shifts that cross midnight, and the time card calculator does the whole week for you.
Step 1: Write down the clock-in and clock-out times
Use the actual punch times, not the scheduled times, unless your employer rounds (see the 7-minute rule). Write AM and PM clearly, or use 24-hour time: 5:00 PM is 17:00.
Step 2: Subtract the start from the end (the subtraction method)
Convert both times to 24-hour format, then subtract hours and minutes separately. If the minutes go negative, borrow 60 from the hours.
| Start | End | Working | Elapsed |
|---|---|---|---|
| 8:00 AM | 4:30 PM (16:30) | 16:30 − 8:00 | 8 h 30 min |
| 9:15 AM | 5:45 PM (17:45) | 17:45 − 9:15 | 8 h 30 min |
| 7:45 AM | 4:10 PM (16:10) | 16:10 − 7:45 → borrow: 15:70 − 7:45 | 8 h 25 min |
| 11:30 AM | 8:05 PM (20:05) | 20:05 − 11:30 → 19:65 − 11:30 | 8 h 35 min |
If the borrowing step trips you up, use the minutes method below.
Step 2, alternative: convert everything to minutes (the decimal method)
Turn each time into minutes past midnight (hours × 60 + minutes), subtract, then divide by 60. There is no borrowing and the result is already ready for decimal conversion.
- 7:45 AM = 7 × 60 + 45 = 465 minutes
- 4:10 PM = 16 × 60 + 10 = 970 minutes
- 970 − 465 = 505 minutes
- 505 ÷ 60 = 8.42 hours (8 hours 25 minutes)
Step 3: Subtract unpaid breaks
Take off the unpaid meal period only. Under the Fair Labor Standards Act, short rest breaks of roughly 5 to 20 minutes are paid time and stay in the total. A meal period of 30 minutes or more can be unpaid only if you were completely relieved of duty for the whole of it. So a 7:45 to 4:10 day with a 30-minute unpaid lunch and two paid 10-minute breaks is 505 − 30 = 475 minutes, or 7.92 hours. If you were called back after 15 minutes of lunch, only 15 minutes come off.
For 12-hour shifts specifically, the 12-hour shift with a 30-minute lunch page has a full table of shift and break combinations.
Step 4: Handle overnight shifts
When the shift ends on the next calendar day, a straight subtraction gives a negative number. Two fixes work:
Add 24 hours to the end time. A 10:00 PM to 6:00 AM shift: 6:00 becomes 30:00. 30:00 − 22:00 = 8 hours.
Split at midnight. 10:00 PM to midnight is 2 hours. Midnight to 6:00 AM is 6 hours. 2 + 6 = 8 hours.
| Shift | To midnight | After midnight | Elapsed | Minus 30-min lunch |
|---|---|---|---|---|
| 10:00 PM – 6:00 AM | 2 h 00 | 6 h 00 | 8 h 00 | 7.50 |
| 11:00 PM – 7:30 AM | 1 h 00 | 7 h 30 | 8 h 30 | 8.00 |
| 7:00 PM – 7:00 AM | 5 h 00 | 7 h 00 | 12 h 00 | 11.50 |
| 9:30 PM – 5:45 AM | 2 h 30 | 5 h 45 | 8 h 15 | 7.75 |
In the minutes method, add 1,440 (24 × 60) to the end time whenever it is smaller than the start time: 6:00 AM = 360 + 1,440 = 1,800; 1,800 − 1,320 = 480 minutes = 8 hours. One more point for overnight workers: the FLSA counts hours in the workweek in which they are actually worked, so an employer must have a consistent rule for which day a shift that straddles midnight belongs to. Most assign the whole shift to the day it started.
Step 5: Convert to decimal hours
Payroll multiplies hours by a rate, so minutes have to become a fraction of an hour: divide by 60. 8 hours 25 minutes is 8 + 25/60 = 8.42. The trap is writing 8.25 for 8:25; that is 8 hours 15 minutes and loses 10 minutes of pay. The hours to decimal chart lists every minute from 1 to 60, and the converter does one value at a time.
Step 6: Add up the week
Calculate each day on its own, then add. Adding in minutes and converting once is the most accurate; adding two-place decimals is usually within a hundredth of an hour.
| Day | In | Out | Unpaid break | Minutes | Decimal |
|---|---|---|---|---|---|
| Mon | 8:00 AM | 4:30 PM | 30 | 480 | 8.00 |
| Tue | 7:45 AM | 4:10 PM | 30 | 475 | 7.92 |
| Wed | 8:05 AM | 5:20 PM | 45 | 510 | 8.50 |
| Thu | 8:00 AM | 6:00 PM | 30 | 570 | 9.50 |
| Fri | 10:00 PM | 6:00 AM | 30 | 450 | 7.50 |
| Total | 2,485 | 41.42 |
2,485 minutes ÷ 60 = 41.42 hours. Under federal law the hours over 40 in this workweek, 1.42 of them, are overtime at 1.5 times the regular rate. A few states also apply a daily threshold, so Thursday's 9.5 hours would carry 1.5 hours of daily overtime in California. The when does overtime start guide covers both, and the overtime pay calculator turns the hours into dollars.
Spreadsheet formula
With start in A2, end in B2, and break minutes in C2, all as time or number cells:
=(MOD(B2-A2,1)*24) - C2/60
MOD(...,1) makes overnight shifts work by wrapping past midnight; multiplying by 24 turns Excel's fraction-of-a-day into hours; C2/60 converts break minutes to hours. Format the result cell as a plain number with two decimals, not as a time, or Excel will show 8.00 hours as 12:00 AM.
Common mistakes
- Reading minutes as hundredths. 8:45 is 8.75, not 8.45. This one error accounts for most timesheet disputes.
- Deducting paid rest breaks. Two 15-minute breaks are 30 minutes of paid time; only the unpaid meal period comes off.
- Deducting a lunch that was worked through. If you were not fully relieved, the time is hours worked.
- Negative overnight results. 6:00 − 22:00 = −16. Add 24 hours or split at midnight.
- AM/PM typos. A day shift ending at 5:00 AM is almost certainly 5:00 PM. Anything over 16 hours in a day deserves a second look.
- Averaging two weeks. 45 hours and 35 hours is not 80 regular hours; the first week has 5 overtime hours.
- Rounding at every step. Keep minutes until the final total, then convert.
Once you have done it by hand once, let the time card calculator do the rest with the same steps.
Frequently asked questions
How do I calculate hours worked with a lunch break?
Find the total time from clock-in to clock-out, then subtract the unpaid lunch. 8:00 AM to 4:30 PM is 8 hours 30 minutes; minus a 30-minute unpaid lunch is 8 hours, or 8.00 in decimal.
How do I calculate hours for an overnight shift?
Add 24 hours to the end time before subtracting, or count to midnight and then from midnight. 10:00 PM to 6:00 AM: from 10 PM to midnight is 2 hours, midnight to 6 AM is 6 hours, total 8 hours.
What is the formula for hours worked?
Hours worked = (clock-out time − clock-in time) − unpaid breaks. Do the subtraction in minutes, then divide by 60 to get decimal hours. In a spreadsheet: =(end − start − break) × 24 when the cells are formatted as times.
How do I convert the minutes to a decimal?
Divide by 60. 8 hours 20 minutes is 8 + 20/60 = 8.33 hours. The full 1-to-60 table is on the hours to decimal chart.
Do 15-minute breaks count as hours worked?
Yes. Under federal rules short rest breaks of about 5 to 20 minutes are paid work time. Only bona fide meal periods of 30 minutes or more, during which you are fully relieved of duty, can be deducted.
How do I total a week of hours?
Work out each day separately (including the lunch deduction), then add the days. Add in minutes and convert the total once, or add decimal hours rounded to two places. Anything over 40 in a single workweek is overtime under federal law.
Can I just use a calculator for this?
Yes. The free time card calculator takes start, end, and break for each day and returns daily and weekly totals in both h:mm and decimal, with overtime split out. This page explains what it is doing.
Last updated 2026-09-16. Everything on this page runs in your browser. Nothing you type or upload leaves your device.