How to Calculate Work Hours: Formulas, Examples and a Free Tool

To calculate work hours, subtract the start time from the end time, then subtract any unpaid break. Do that for each day, add the daily totals, and convert minutes to decimals (minutes divided by 60) if payroll needs a number like 7.75. A shift from 9:15 a.m. to 6:00 p.m. with a one-hour unpaid lunch is 7 hours 45 minutes, or 7.75 hours. The rest of this guide covers the cases that trip people up: breaks, overnight shifts, weekly totals, rounding and overtime.

TL;DR

• Hours worked = clock-out time minus clock-in time minus unpaid breaks. Write times in 24-hour format to avoid a.m./p.m. mistakes.
• To convert minutes to decimal hours, divide by 60: 45 minutes is 0.75, so 7 h 45 min is 7.75 hours.
• Under U.S. federal rules, short rest breaks (usually 20 minutes or less) count as work time, while real meal periods of 30 minutes or more generally do not.
• For a shift past midnight, add the time left until midnight to the time after it, or use a spreadsheet MOD formula.
• Our free hours calculator does the subtraction, breaks and weekly total in your browser, with no sign-up.

Table of Contents

• The basic formula for hours worked
• How to handle breaks
• Calculating a shift that crosses midnight
• Adding up a full week
• Converting minutes to decimal hours
• Rounding punches: what is allowed
• Overtime and how it changes the count
• Three ways to calculate work hours
• Perspective
• Common mistakes to avoid
• Try the calculator on your own timesheet
• FAQ
• Sources

The basic formula for hours worked

Every method comes down to one line:

Hours worked = (end time − start time) − unpaid break time

The standard advice is to record the exact clock-in and clock-out times, convert them to 24-hour time and subtract the start from the end, then take off unpaid breaks. The 24-hour clock matters because it removes the a.m./p.m. step where most errors happen. 5:00 p.m. becomes 17:00, and 17:00 minus 09:00 is plainly 8 hours.

A worked example, step by step

Say you clocked in at 8:30 a.m. and out at 5:15 p.m., with a 45-minute unpaid lunch.

1. Convert to 24-hour time: 08:30 and 17:15.
2. Subtract the hours: 17 − 8 = 9 hours. Subtract the minutes: 15 − 30 = −15 minutes.
3. Borrow an hour to fix the negative: 9 hours − 15 minutes = 8 hours 45 minutes.
4. Subtract the 45-minute break: 8 hours 45 minutes − 45 minutes = 8 hours 0 minutes.

The borrowing in step 3 is the part people forget. A faster way is to convert both times to minutes since midnight: 08:30 is 510 minutes and 17:15 is 1,035 minutes. The difference is 525 minutes. Minus 45 is 480 minutes, which is 8 hours.

Checking your answer

A quick sanity test: count up from the start time in whole hours, then add the leftover minutes. From 08:30, nine hours gets you to 17:30, which is 15 minutes too far. So the span is 9 hours minus 15 minutes, matching step 3. If your answer doesn’t pass a count-up check, redo the subtraction before it reaches a timesheet.

How to handle breaks

Whether a break comes off your total depends on whether it is paid. In the U.S., the Department of Labor’s guidance on hours worked says rest periods of about 20 minutes or less are normally counted as hours worked, and that bona fide meal periods, typically 30 minutes or more, generally do not have to be paid when the employee is completely relieved from duty.

In practice:

The last row surprises people. Work that is suffered or permitted counts even when it was not requested. If you are an employee and your total looks short, check whether a lunch you spent answering messages was subtracted.

State laws and employer policies can be stricter than the federal rule, and some states require meal or rest breaks. For a specific situation, check your state labor department or ask your payroll team.

Calculating a shift that crosses midnight

When the end time is earlier than the start time, straight subtraction goes negative. A night shift from 22:00 to 06:30 is the classic case.

By hand: split the shift at midnight. From 22:00 to 24:00 is 2 hours. From 00:00 to 06:30 is 6 hours 30 minutes. Total: 8 hours 30 minutes, or 8.5 hours.

In a spreadsheet: times are stored as fractions of a day, so you multiply by 24 to get hours. For shifts that span midnight, the MOD function handles the wraparound: =MOD(End-Start,1)*24. With the start in A2 and end in B2, that returns 8.5 for the example above. For ordinary same-day shifts, =(B2-A2)*24 is enough.

If the shift also crosses a date line that matters for pay periods, or you need the number of days between two dates rather than hours, our date difference calculator covers that side.

Adding up a full week

Calculate each day’s net time first, after that day’s break, then add the days. Don’t add raw spans and subtract a single weekly break at the end, because breaks differ from day to day.

Here is a sample week:

Add in decimals: 8 + 7.75 + 8.25 + 8 + 6.5 = 38.5 hours. If you add in hours and minutes instead, remember that 60 minutes rolls over to a new hour. Adding 7:45 and 8:15 gives 16:00, not 15:60.

Converting minutes to decimal hours

Payroll systems pay by the hour as a decimal, so 7 hours 45 minutes has to become 7.75. The method: divide the minutes by 60 and add the result to the whole hours. Forty-five minutes is 45 ÷ 60 = 0.75.

A reference table saves repeating the division:

Values like 0.33 and 0.67 are rounded. For payroll, the usual practice is rounding decimal hours to the nearest hundredth. The common mistake is to read 7:45 as 7.45. It is not: 7.45 hours is 7 hours 27 minutes. That one slip on a 40-hour week can shift a paycheck noticeably.

Going the other way, multiply the decimal part by 60. For 38.5 hours, 0.5 × 60 = 30, so it is 38 hours 30 minutes. If you need to scale a rate or split a total, our percentage calculator and fraction calculator are handy for the surrounding arithmetic.

Rounding punches: what is allowed

Many time clocks round to the nearest 5 minutes, tenth of an hour or quarter hour. Federal regulation says this practice is accepted for enforcement purposes as long as it does not, over time, result in employees failing to be paid for all the time they actually worked. In other words, rounding has to average out. A rule that always rounds down in the employer’s favor is the problem, not rounding itself.

The familiar quarter-hour approach treats the first 7 minutes past a quarter as rounding down and 8 or more as rounding up. If you are checking your own pay, work out the exact figure first, then compare it with what your employer’s system produced. If the gap is consistently in one direction, raise it with payroll, and with your state labor department if it is not resolved.

Overtime and how it changes the count

The weekly total matters because of overtime. Under the federal Fair Labor Standards Act, overtime applies after 40 hours in a workweek for covered, non-exempt employees. A workweek is a fixed, recurring period of 168 hours, so it is the same seven days every time, not a rolling window.

Suppose your week totals 42.5 hours. Regular hours are 40 and overtime hours are 2.5. The overtime premium is paid at a higher rate (the federal minimum is one and a half times your regular rate), so splitting the total correctly is what protects your pay. Exempt roles, state daily-overtime rules and union contracts can change this, so confirm with your employer or your state labor department.

For a quick pay estimate, multiply regular hours by your rate, multiply overtime hours by your rate times 1.5, and add the two. At $20 an hour: 40 × $20 = $800, plus 2.5 × $30 = $75, for $875 before taxes.

Three ways to calculate work hours

1. By hand. Fine for one shift. Convert to 24-hour time, subtract, take off the break. It breaks down over a full week, where carrying minutes becomes error-prone.

2. A spreadsheet. Good if you already keep a timesheet. Use =(End-Start)*24 for same-day shifts and the MOD version for overnight ones, then format the result as a number with two decimals. Remember to subtract the break in hours (30 minutes is 0.5, or 30/60).

3. An online hours calculator. The fastest option for a weekly timesheet. You enter start and end times, set the break, and the tool totals each day and the week. Look for one that shows both hours-and-minutes and decimal results, since you will usually need both.

Perspective

We built the hours calculator because this is a job people do in a hurry: it is Friday afternoon, a timesheet is due, and nobody wants to open a spreadsheet or create an account for one subtraction.

Our view is that a time tool should do three things well. It should take times the way you think of them, like 8:30 and 5:15. It should show the answer both ways, hours and minutes plus decimal, because the two are used in different places. And it should keep your numbers private. Our tools are designed to process data locally in your browser, so your work times are not something you have to hand over to get a total.

We also think the explanation matters as much as the answer. If you know why 7:45 is 7.75 and not 7.45, you can spot a payroll mistake yourself. That is why this guide sits next to the calculator.

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Common mistakes to avoid

• Reading minutes as decimals. 7:45 is 7.75, not 7.45. Always divide minutes by 60.
• Mixing 12-hour and 24-hour time. 12:30 a.m. is 00:30 and 12:30 p.m. is 12:30. Mixing these up creates 12-hour errors.
• Subtracting breaks that were paid. Short rest breaks normally count, so only subtract the true off-duty meal period.
• Ignoring work done off the clock. Time spent finishing a task after you punch out is still work time.
• Adding in base 10. When adding hours and minutes, carry at 60. Two entries of 0:40 make 1:20, not 0:80.
• Using a calendar week instead of the workweek. Overtime follows the employer’s fixed workweek, which may start on a Sunday, Monday or another day.

Try the calculator on your own timesheet

If you would rather not do the subtraction by hand, open our hours calculator and enter your start and end times and your break for each day. It gives daily and weekly totals you can copy straight into a timesheet, and it works on a phone as well as a desktop.

It is free to use with no download or sign-up. If you want advanced features and no ads, Easy App Library Pro costs $2.49 per month, or you can pay $17.99 once for Lifetime. You can compare the plans on our pricing page, or browse the rest of our free calculators. Pairing it with a Pomodoro timer or our stopwatch is a simple way to track focused work as it happens.

FAQ

How do I work out hours worked if I forgot to log my breaks?

Start with your clock-in and clock-out times, then subtract only the unpaid, fully off-duty meal period you actually took. Short rest breaks of about 20 minutes or less are normally counted as paid time, so they stay in. If you are unsure what your employer treats as unpaid, check your handbook or ask payroll.

How do I calculate hours worked from 7 a.m. to 3:30 p.m.?

Convert to 24-hour time: 07:00 to 15:30 is 8 hours 30 minutes. If you took a 30-minute unpaid lunch, subtract it to get 8 hours, or 8.00 decimal hours. With no unpaid break, the total is 8.5 hours.

How do I convert 8 hours 20 minutes to decimal?

Divide the minutes by 60: 20 ÷ 60 = 0.33 when rounded to the nearest hundredth. Add that to the 8 whole hours to get 8.33 hours. Remember that this is rounded, so multiplying 8.33 back by 60 gives a minute or so less than the exact figure.

Can my employer round my time?

Often yes. Federal regulation accepts rounding to the nearest 5 minutes, tenth or quarter of an hour, provided it does not result over time in underpaying employees for the time they worked. If your rounded pay is always lower than your exact hours, raise it with payroll or your state labor department.

When does overtime start?

For covered, non-exempt employees, federal overtime applies after 40 hours in a workweek. Some states also have daily overtime or different rules, so check your state labor department for your own situation.

Sources

• Fact Sheet #22: Hours Worked Under the Fair Labor Standards Act, U.S. Department of Labor
• 29 CFR § 785.48, Use of time clocks
• How To Calculate Hours Worked: Formula and Examples
• Calculate Number of Hours Between Times in Excel and Google Sheets

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• Hours Calculator: Time Card & Work Hours

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