To calculate hours worked, subtract the start time from the end time, then subtract any unpaid break. A shift from 8:30 a.m. to 5:15 p.m. is 8 hours 45 minutes; take off a 45-minute lunch and you worked 8 hours, or 8.00 in decimal hours.
That one subtraction covers most timesheets, but a few things trip people up: shifts that cross midnight, minutes that have to become decimals for payroll, weekly totals and the nights when the clocks change. This guide walks through each case with worked examples you can check against our hours calculator, which handles breaks, overnight shifts and weekly or biweekly timesheets for you.
How to calculate hours worked, step by step
- Write both times on a 24-hour clock. 8:30 a.m. stays 08:30; 5:15 p.m. becomes 17:15. This removes the a.m./p.m. guesswork. Our 24-hour time chart lists every hour if you need it.
- Subtract the minutes, then the hours. 17:15 minus 08:30: 15 minus 30 doesn’t work, so borrow an hour. 75 minus 30 is 45 minutes, and 16 minus 8 is 8 hours. The span is 8 hours 45 minutes.
- Take off unpaid breaks. 8 hours 45 minutes minus a 45-minute lunch is 8 hours 0 minutes.
- Convert to decimal hours if payroll asks for it. Divide the leftover minutes by 60. Here there are none, so the answer is 8.00 hours.
The step people most often get wrong is the last one. 8 hours 45 minutes is 8.75 hours, not 8.45, because 45 minutes is three-quarters of an hour. Our minutes to decimal hours chart has every value from 1 to 60.
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 you subtract.
- Example: 10:00 p.m. to 6:45 a.m. with a 30-minute break. On a 24-hour clock that is 22:00 to 06:45. Add 24 hours to the end: 30:45. Then 30:45 minus 22:00 is 8 hours 45 minutes. Subtract the break and you get 8 hours 15 minutes, or 8.25 hours.
Another way to see it: count from the start time to midnight (2 hours), then from midnight to the end time (6 hours 45 minutes), and add the two. Both methods give the same answer. Most timesheets credit the whole shift to the day it started, which is also how our hours calculator totals a week.
Breaks: paid or unpaid
Only subtract the breaks your employer doesn’t pay for. Under the federal Fair Labor Standards Act, the US Department of Labor’s rules describe short rest periods of about 5 to 20 minutes as counted as hours worked, while a bona fide meal period, ordinarily 30 minutes or more with the employee fully relieved of duties, is not usually work time. Some states add their own break rules, and contracts vary, so check your local labor rules and your employer’s policy before you decide what to subtract.
If you split a day into two shifts, for example a morning and an evening shift, work out each one on its own and add them. The hours calculator lets you enter two shifts per day for this reason.
A weekly timesheet, worked out
Here is one workweek, Monday, October 5 to Friday, October 9, 2026, with an unpaid break each day:
| Day | Start | End | Unpaid break | Hours worked | Decimal |
|---|---|---|---|---|---|
| Monday, Oct 5 | 8:00 a.m. | 4:30 p.m. | 30 min | 8 h 0 min | 8.00 |
| Tuesday, Oct 6 | 8:00 a.m. | 5:15 p.m. | 30 min | 8 h 45 min | 8.75 |
| Wednesday, Oct 7 | 7:45 a.m. | 4:00 p.m. | 30 min | 7 h 45 min | 7.75 |
| Thursday, Oct 8 | 8:00 a.m. | 6:00 p.m. | 45 min | 9 h 15 min | 9.25 |
| Friday, Oct 9 | 8:00 a.m. | 3:20 p.m. | 20 min | 7 h 0 min | 7.00 |
| Week total | 40 h 45 min | 40.75 |
Add the hours and minutes separately and carry every 60 minutes into an hour: 39 hours plus 105 minutes is 39 hours plus 1 hour 45 minutes, or 40 hours 45 minutes. Adding the decimal column gives the same 40.75, which is a good cross-check.
Overtime and the workweek
For employees covered by the FLSA, the Department of Labor says overtime is due for hours worked over 40 in a workweek at not less than one and a half times the regular rate. A workweek is a fixed, recurring period of 168 hours (seven consecutive 24-hour periods), and hours can’t be averaged across two or more weeks.
In the example above, 40.75 hours means 0.75 hours (45 minutes) over 40. If you’re paid every two weeks, total each week separately: a 45-hour week followed by a 35-hour week still includes 5 overtime hours, even though the two weeks average 40. Some states and contracts set daily overtime or different thresholds, so check what applies to you. Our hours calculator counts overtime week by week, and the 2026 payday calendar shows where each pay period starts and ends.
When the clocks change mid-shift
Night shifts on a daylight saving weekend are the one case where the clock on the wall gives the wrong answer.
- Fall back: a shift from 10:00 p.m. on Saturday, October 31, 2026 to 6:00 a.m. on Sunday, November 1 looks like 8 hours, but clocks go back an hour at 2:00 a.m., so the worker is on the job for 9 hours.
- Spring forward: the same shift from Saturday, March 13 to Sunday, March 14, 2027 lasts only 7 hours, because the hour from 2:00 to 3:00 a.m. is skipped.
The daylight saving time guide lists every change through 2030. For any span that includes dates as well as times, the time duration calculator counts real elapsed time.
Doing it in a spreadsheet
Spreadsheets store times as fractions of a day, so multiply by 24 to get hours. With the start time in B2, the end time in C2 and the unpaid break in minutes in D2:
=(MOD(C2-B2,1)-D2/1440)*24gives decimal hours, including shifts that cross midnight. MOD wraps a negative result back into the same day, and dividing the break by 1,440 (the minutes in a day) turns it into a fraction of a day.- Format the cell as a number, not a time, or you’ll see a clock value instead of 8.25.
- For a weekly total in hours and minutes, sum the time values and use the custom format
[h]:mm, which stops the total from wrapping back to zero after 24 hours.
To add up a column of durations by hand, or subtract one length of time from another, use the time calculator.
Frequently asked questions
How do I calculate hours worked with a lunch break?
Subtract the start time from the end time, then subtract the length of the unpaid lunch. For 8:00 a.m. to 4:30 p.m. with a 30-minute lunch, that is 8 hours 30 minutes minus 30 minutes, so 8 hours.
How do I convert hours and minutes to decimal hours?
Divide the minutes by 60 and add the result to the whole hours. 7 hours 45 minutes is 7 + 45 ÷ 60 = 7.75 hours, and 7 hours 20 minutes is about 7.33 hours.
How many hours is 9 a.m. to 5 p.m.?
Eight hours. If a 30-minute lunch is unpaid, it is 7 hours 30 minutes, or 7.5 hours, of paid time.
How do I calculate hours for an overnight shift?
Add 24 hours to the end time, then subtract the start time. 11:00 p.m. to 7:00 a.m. becomes 31:00 minus 23:00, which is 8 hours.
Can my employer round my time punches?
Federal rules allow rounding to the nearest 5 minutes, tenth or quarter of an hour only if it doesn’t, over time, underpay employees for time they actually worked. State laws can be stricter, so check your local labor rules.