Hours Calculator

Hours between a start and end time

The hours calculator converts both times to minutes after midnight and subtracts the start from the end. For a shift from 9:00 to 17:30, that is 1,050 − 540 = 510 minutes, or 8 hours 30 minutes. Any unpaid break is then subtracted to give the time worked.

Times are entered on a 24-hour basis, although your browser may display the field in 12-hour format with AM and PM. Midnight is 00:00 and noon is 12:00.

How to calculate hours worked by hand

The same steps work on paper. Take a shift from 9:20 to 18:05 with a 40-minute unpaid lunch.

1. Convert each time to minutes after midnight. 9:20 is 9 × 60 + 20 = 560. 18:05 is 18 × 60 + 5 = 1,085.
2. Subtract the start from the end. 1,085 − 560 = 525 minutes, which is 8 hours 45 minutes.
3. Take off the unpaid break. 525 − 40 = 485 minutes, or 8 hours 5 minutes.
4. Convert to decimal hours. 485 ÷ 60 = 8.0833…, which rounds to 8.08 hours.

An alternative is to borrow an hour when the end minutes are smaller than the start minutes: 18:05 becomes 17:65, and 17:65 − 9:20 = 8:45. Both methods give the same answer.

Working out hours with a lunch break

Enter an unpaid lunch or other break in minutes, and it is taken off the time between clocking in and clocking out. A 7:30 to 16:00 shift is 8 hours 30 minutes on the clock. With a 30-minute unpaid lunch, the time worked is 8 hours, or 8.00 decimal hours. If you take two unpaid breaks, add them together and enter the total. Paid rest breaks stay in the total, so leave them out of the break field.

Overnight shifts

When a shift crosses midnight, the end time is a smaller number than the start time. Subtracting would give a negative answer, so the calculator adds 24 hours to the end time first. A shift from 23:00 to 07:00 becomes 07:00 + 24 h − 23:00 = 8 hours. A note under the result tells you when this has happened.

By hand, split the shift at midnight. From 21:40 to midnight is 2 hours 20 minutes, and from midnight to 05:10 is 5 hours 10 minutes, for a total of 7 hours 30 minutes, or 7.5 hours.

If you clock in and out at exactly the same time, the hours calculator reads this as a full 24-hour shift rather than zero.

Converting hours and minutes to decimal hours

Payroll systems and timesheets usually record time as decimal hours, because hourly pay is hours multiplied by a rate. To convert, divide the minutes by 60.

A common mistake is to read 7 hours 30 minutes as 7.30. In decimal form it is 7.5 hours, and paying it as 7.3 hours would short the worker 12 minutes.

Adding up a week

For a weekly total, run each day through the calculator and add the results. Here is an example week with unpaid breaks already deducted:

The total is 2,385 minutes, which is 39 hours 45 minutes or exactly 39.75 hours. Adding the rounded daily figures instead gives 39.76, because each day’s rounding adds a little. For the most accurate total, add the minutes first and convert to decimal once at the end. If you need to see what share of a target the total represents, such as hours against a 40-hour week, the percentage calculator can help.

Rounding, breaks and overtime

Many employers record clock times to the nearest 5 minutes, tenth of an hour (6 minutes) or quarter hour (15 minutes). US federal rules allow this kind of rounding only if, over time, it doesn’t result in employees being underpaid for the time they actually worked. With quarter-hour rounding, a common approach is to round 1 to 7 minutes down and 8 to 14 minutes up, so a 7:53 clock-in is recorded as 8:00 and an 8:07 clock-in is also recorded as 8:00.

Federal law doesn’t require meal or rest breaks, but many states do, and short rest breaks are generally treated as paid time under the Fair Labor Standards Act. Overtime under federal law starts after 40 hours in a workweek, and some states also have daily limits. These rules vary by state, industry and contract, so use the calculator for the arithmetic and check the rules that apply to you. The guide to how to calculate hours worked covers timesheets and these rules in more depth. Nothing on this page is payroll or legal advice.

Tips and common mistakes

• Mixing up 12 AM and 12 PM. 12 AM is midnight and 12 PM is noon. Getting them backwards adds or removes 12 hours.
• Writing minutes as decimals. 8 hours 20 minutes is 8.33 hours, not 8.20.
• Deducting paid breaks. Only enter unpaid time in the break field.
• Daylight saving time. The calculator doesn’t model clock changes. A night shift on the night the clocks go forward or back is an hour shorter or longer in real time than the clock times suggest.
• Overnight entries on paper. Note the date on both ends of a shift that crosses midnight so the hours are assigned to the right day or workweek.

Glossary

• Decimal hours. Time written as a decimal number of hours, such as 7.75 for 7 hours 45 minutes.
• Unpaid break. Time off duty that isn’t counted as hours worked, usually a meal period.
• Workweek. Under US federal law, a fixed, recurring period of 168 hours, or seven consecutive 24-hour periods. It need not start on a Monday.
• Overnight shift. A shift whose end time is on the next calendar day.

To count calendar days rather than clock hours, use the days between dates calculator.