How to calculate hours worked, step by step

To calculate hours worked, take the time you stopped, subtract the time you started, then subtract any unpaid meal break. The AlarmPick hours calculator does that arithmetic for one shift and shows the answer in hours and minutes and as decimal hours. This guide shows the same steps by hand, so you can check a timesheet or add up a full week.

The short answer

Use this order for each shift:

1. Write the start time and the end time in 24-hour form, such as 08:45 and 17:15.
2. Find the span between them. 08:45 to 17:15 is 8 hours 30 minutes.
3. Subtract unpaid meal breaks. A 30-minute lunch leaves 8 hours 0 minutes.
4. Leave short rest breaks in. Federal rules count them as hours worked.
5. Convert the result to decimal hours if your timesheet asks for it. 8 hours 0 minutes is 8.00.

Then add the daily totals for the week. That weekly total is the number that matters for overtime under the Fair Labor Standards Act.

Work out the span between two times

The simplest method is to turn both times into minutes after midnight. Multiply the hours by 60 and add the minutes.

• 08:45 is 8 × 60 + 45 = 525 minutes.
• 17:15 is 17 × 60 + 15 = 1,035 minutes.
• 1,035 − 525 = 510 minutes.
• 510 minutes is 8 hours 30 minutes.

If you use a 12-hour clock, convert first. 5:15 p.m. becomes 17:15. Midnight is 00:00 and noon is 12:00. Most mistakes on paper timesheets come from mixing a.m. and p.m., so convert every time before you subtract.

Subtract meal breaks, but not short rest breaks

Not every break comes off the total. Federal rules treat short rest breaks and real meal periods differently.

Under 29 CFR 785.18, rest periods of about 5 to 20 minutes "must be counted as hours worked." Under 29 CFR 785.19, a meal period is not worktime only when you are completely relieved from duty to eat. Coffee breaks and snack breaks are rest periods, not meal periods. The same section gives the example of an office worker required to eat at their desk: that person is working while eating.

So, for a shift from 08:45 to 17:15 with a 30-minute lunch away from work and two 10-minute coffee breaks, subtract only the lunch. The total is 8 hours 0 minutes.

Shifts that cross midnight

When the end time is earlier than the start time, the shift ran past midnight. Split it in two:

1. From the start to midnight. 22:00 to 24:00 is 2 hours.
2. From midnight to the end. 00:00 to 06:30 is 6 hours 30 minutes.
3. Add the parts: 8 hours 30 minutes.
4. Subtract an unpaid meal break of 30 minutes: 8 hours 0 minutes.

The hours calculator does this for you. If the end time is earlier than the start, it treats the end as the next day. It does not adjust for the night the clocks change, so check that night by hand.

Convert hours and minutes to decimal hours

Payroll systems often want 7.75 rather than 7 hours 45 minutes. To convert, divide the minutes by 60 and add the result to the whole hours.

For example, 7 hours 20 minutes is 7 + 20 ÷ 60 = 7.33 hours. Do the rounding once, at the end. If you round every day before you add, small errors can build up over a week.

When an employer rounds clock times

Some workplaces record start and stop times to the nearest 5 minutes, tenth of an hour or quarter hour. 29 CFR 785.48 describes this practice. It is accepted for enforcement only when it does not, over a period of time, leave employees unpaid for time they actually worked.

With rounding to the nearest quarter hour, a punch at 08:53 becomes 09:00 and a punch at 09:07 also becomes 09:00. If you want to compare your own record with a rounded timesheet, keep the exact times and total them yourself.

Add up a full workweek

The workweek is not always Monday to Sunday. Under 29 CFR 778.105, it is a fixed, regularly recurring period of 168 hours, seven consecutive 24-hour periods. It can begin on any day and at any hour.

Here is a week with a 30-minute unpaid lunch every day:

Under 29 CFR 778.101, 40 hours is the general maximum an employee covered by the Act may work in a workweek without overtime pay. In this example, 1.50 hours are over that line. Section 778.107 sets overtime at not less than one and one-half times the employee's regular rate.

Each workweek stands on its own. 29 CFR 778.104 says the Act does not permit averaging hours over two or more weeks. A 30-hour week followed by a 50-hour week still has overtime in the second week.

Use the AlarmPick hours calculator

1. Open the hours calculator.
2. Enter the start time and the end time for one shift.
3. Pick a break chip of 0, 15, 30 or 60 minutes, or type the unpaid break in minutes.
4. Choose Calculate. Read the net duration and the decimal hours.
5. Repeat for each day and add the decimal results for the week.

The calculator measures clock time only. It does not attach a date, apply daylight saving time, decide pay or judge overtime. The times you enter are not saved.

FAQ

Do I subtract a 15-minute break from my hours?

Usually not. Under federal rules, rest breaks of about 5 to 20 minutes count as hours worked. Only a meal period where you are completely relieved from duty comes off.

Does overtime start after 8 hours in a day?

Not under the federal rule this guide quotes. The Fair Labor Standards Act measures overtime by the workweek, with 40 hours as the general maximum before overtime pay.

What records should a timesheet show?

29 CFR 516.2 lists the hours worked each workday and the total hours worked each workweek among the records an employer keeps for covered employees.

Why does my total differ from my payslip by a few minutes?

Your employer may round clock times to the nearest 5 minutes, tenth or quarter hour. That is allowed only if, over time, it does not leave you unpaid for time you worked.

Sources

• 29 CFR 785.18: Rest
• 29 CFR 785.19: Meal
• 29 CFR 785.48: Use of time clocks
• 29 CFR 778.101: Maximum nonovertime hours
• 29 CFR 778.104: Each workweek stands alone
• 29 CFR 778.105: Determining the workweek
• 29 CFR 778.107: General standard for overtime pay
• 29 CFR 516.2: Records for employees subject to minimum wage or overtime provisions