How to calculate hours worked

6 October 2026 · Calcosmo editorial team

To calculate hours worked, take your end time minus your start time, then subtract unpaid breaks. From 8:45 am to 5:15 pm with a 30-minute lunch is 8 hours. For payroll, convert the minutes to decimals by dividing by 60: 7 hours 45 minutes is 7.75 hours. Add up a whole time card with the hours calculator.

Step 1: use a 24-hour clock

Mixing am and pm is the most common source of mistakes. Convert to 24-hour time first: 5:15 pm becomes 17:15. Now subtracting is straightforward.

Step 2: subtract start from end

17:15 − 08:45. If the end minutes are smaller than the start minutes, borrow an hour:

• 17:15 = 16:75
• 16:75 − 08:45 = 8:30

Step 3: subtract unpaid breaks

8:30 − 0:30 lunch = 8:00 hours worked. Paid breaks stay in.

Step 4: convert to decimal hours

Payroll and invoices use decimal hours. Divide the minutes by 60:

So 7:45 is 7.75 hours, not 7.45. At $22 an hour, the difference between 7.45 and 7.75 is $6.60 for one day.

A weekly time card

37 hours 55 minutes is 37.92 decimal hours. Do not add the times as ordinary numbers: 8.25 + 7.30 is not the same as 8:25 + 7:30. Adding hours and minutes separately and carrying 60 minutes to an hour avoids the error, and the hours calculator does it for you.

Overnight shifts

For a shift that crosses midnight, add 24 hours to the end time. From 22:00 to 06:30: 30:30 − 22:00 = 8:30. Minus a 30-minute break gives 8 hours.

Overtime

Overtime rules differ by country and contract. In the US, the Fair Labor Standards Act requires time and a half for non-exempt employees after 40 hours in a workweek. With the time card above (37.92 hours) there is no overtime. Some states, such as California, also have daily overtime rules. In the UK and the Netherlands, overtime pay is set by your contract or collective agreement rather than one national rule.

Rounding

Many time clocks round to the nearest 5, 6 or 15 minutes. In the US, rounding is allowed as long as it is neutral over time and does not systematically favour the employer. When in doubt, record exact times.