How to Calculate Hours Worked

Working out hours from a timesheet is simple arithmetic, but a few details cause most of the errors: minutes written as decimals, shifts that cross midnight, breaks that may or may not be paid, and rounding. This guide walks through the method step by step, using US federal rules as a reference point where they help. It explains the arithmetic, not the law. Rules on breaks, rounding and overtime vary by state, industry and contract, so treat it as general information rather than payroll or legal advice.

Step 1: Record start and end times

Start with the clock times for each shift, written in 24-hour format if possible. It avoids the most common mix-up, 12 AM and 12 PM. On a 24-hour clock, midnight is 00:00, noon is 12:00, and 3:30 PM is 15:30.

Write the date next to each time, especially for night work. A shift that starts at 22:00 on Monday and ends at 06:15 on Tuesday is one shift, and having both dates on the record makes it clear which day and which workweek it belongs to.

The US Department of Labor’s recordkeeping fact sheet says employers must keep records of hours worked each day and total hours worked each workweek, and that any timekeeping method is acceptable as long as it is complete and accurate. A time clock, an app or a paper sheet can all work.

Step 2: Work out the length of each shift

Convert each time to minutes after midnight by multiplying the hours by 60 and adding the minutes. Then subtract the start from the end.

For a shift from 07:40 to 16:10:

• 07:40 is 7 × 60 + 40 = 460 minutes.
• 16:10 is 16 × 60 + 10 = 970 minutes.
• 970 − 460 = 510 minutes, which is 8 hours 30 minutes.

Working in minutes avoids the borrowing that makes subtracting hours and minutes awkward. The hours calculator does exactly this and shows the step.

Overnight shifts

If the end time is earlier than the start time, the shift crossed midnight. Add 24 hours (1,440 minutes) to the end time before subtracting. For 22:00 to 06:15, that is 375 + 1,440 − 1,320 = 495 minutes, or 8 hours 15 minutes.

An easy check is to split the shift at midnight: 22:00 to midnight is 2 hours, and midnight to 06:15 is 6 hours 15 minutes, for the same total.

Long on-duty periods have their own rules. The Department of Labor explains that employees on duty for 24 hours or more may, under certain conditions, agree to exclude a regularly scheduled sleeping period of up to 8 hours. Situations like that call for the specific rules rather than simple clock arithmetic.

Step 3: Subtract unpaid breaks

Subtract only time that is genuinely unpaid. Under the federal Fair Labor Standards Act:

• Short rest breaks, usually about 5 to 20 minutes, are counted as hours worked.
• Bona fide meal periods, typically 30 minutes or more, generally don’t count, but only if the employee is completely relieved from duty. Eating at your desk while answering calls is work time.

Federal law doesn’t require employers to give meal or coffee breaks at all. Many states do require meal periods, and the Department of Labor publishes a state-by-state table, so the rule depends on where the work is done.

Continuing the overnight example, 495 minutes minus a 30-minute unpaid meal break leaves 465 minutes worked.

Step 4: Convert to decimal hours

Payroll uses decimal hours because pay is hours multiplied by an hourly rate. Divide minutes by 60: 465 ÷ 60 = 7.75 hours.

The minutes part is the common source of errors. Quarter hours are easy (15 minutes is 0.25, 30 is 0.5 and 45 is 0.75), but other values aren’t:

Minutes	Decimal hours
6	0.1
10	0.17
20	0.33
25	0.42
40	0.67
50	0.83

So 7 hours 40 minutes is 7.67 hours, not 7.40. To go the other way, multiply the decimal part by 60: 0.42 hours is about 25 minutes.

Step 5: Total the workweek

Add up each shift in the workweek. Under federal law, a workweek is a fixed, regularly recurring period of 168 hours, seven consecutive 24-hour periods. It can start on any day and at any hour, so it doesn’t have to match the calendar week.

Here is a week of mostly night shifts, with unpaid meal breaks already taken off:

Shift starts	Start	End	Unpaid break	Time worked	Decimal hours
Monday	22:00	06:15	30 min	7 h 45 min	7.75
Tuesday	22:00	06:00	30 min	7 h 30 min	7.50
Wednesday	21:45	06:20	30 min	8 h 05 min	8.08
Thursday	22:00	07:10	45 min	8 h 25 min	8.42
Friday	22:05	06:00	30 min	7 h 25 min	7.42
Saturday	18:00	23:30	none	5 h 30 min	5.50

The total is 2,680 minutes, or 44 hours 40 minutes. In decimal hours that is 44.666…, which rounds to 44.67. Adding the rounded daily figures happens to give 44.67 here too, but that isn’t guaranteed. Small rounding differences on each day can add up, so total the minutes first and convert once.

Rounding clock times

Some employers round clock-in and clock-out times. Federal regulations note that recording times to the nearest 5 minutes, or to the nearest tenth or quarter of an hour, is a long-standing practice. It is accepted as long as, over time, it doesn’t result in employees being paid for less time than they actually worked. In practice this means rounding has to go both ways, not only in the employer’s favor.

With quarter-hour rounding, a common approach is to round 7 minutes or less down and 8 minutes or more up:

Clock time	Nearest quarter hour	Nearest tenth of an hour (6 min)
07:53	08:00	07:54
08:07	08:00	08:06
08:08	08:15	08:06
16:52	16:45	16:54
17:06	17:00	17:06

Rounding is a policy choice that sits on top of the arithmetic. Calculate exact times first, then apply whatever rounding rule your workplace uses, and check that it is allowed where you work.

From hours to pay

Once you have decimal hours, gross pay for straight-time work is hours × hourly rate. Under the FLSA, covered nonexempt employees must be paid at least one and a half times their regular rate for hours over 40 in a workweek. Hours can’t be averaged across weeks, so a 44-hour week followed by a 36-hour week still includes 4 overtime hours.

Using the example week and an illustrative rate of $20 an hour, 44 hours 40 minutes is 40 regular hours plus 4 hours 40 minutes of overtime. That works out to 40 × $20 = $800, plus 4⅔ × $30 = $140, for $940 before deductions. Some states add daily overtime or other rules, contracts may be more generous, and the “regular rate” can include more than the base hourly wage, so check the rules that apply. The percentage calculator can help with related questions, such as what share of a 40-hour week a shift represents.

Common mistakes

• Reading minutes as decimals. 8:20 is 8.33 hours, not 8.2.
• Mixing up 12 AM and 12 PM. One way gives a 12-hour error.
• Deducting paid breaks. Short rest breaks are usually paid time under federal law.
• Forgetting to add 24 hours for overnight shifts. A negative result or a suspiciously long shift is the giveaway.
• Rounding each day before totaling. Small differences compound over a pay period.
• Ignoring clock changes. On the night daylight saving time starts or ends, a shift’s real length differs from the clock times by an hour.

Summary

Convert each time to minutes, subtract start from end (adding 24 hours if the shift crosses midnight), take off unpaid breaks, divide by 60, and total the workweek before converting or rounding. The hours calculator handles each shift, and the days between dates calculator helps when you need to count the days in a pay period. For more calculators like these, see the time and date hub.

Sources

1. Fact Sheet #22: Hours Worked Under the Fair Labor Standards Act (FLSA) — U.S. Department of Labor, Wage and Hour Division. Checked October 4, 2026.
2. Fact Sheet #21: Recordkeeping Requirements under the Fair Labor Standards Act (FLSA) — U.S. Department of Labor, Wage and Hour Division. Checked October 4, 2026.
3. Breaks and Meal Periods — U.S. Department of Labor. Checked October 4, 2026.
4. Minimum Length of Meal Period Required under State Law for Adult Employees in Private Sector — U.S. Department of Labor, Wage and Hour Division. Checked October 4, 2026.
5. Overtime Pay — U.S. Department of Labor, Wage and Hour Division. Checked October 4, 2026.
6. 29 CFR § 785.48 — Use of time clocks — Legal Information Institute, Cornell Law School. Checked October 4, 2026.