How to calculate hours worked between two times

Calculating hours worked between two times looks trivial until you actually try it. Clock times are written in base 60, not base 10, so you cannot just subtract 5:30 from 8:15 the way you subtract regular numbers. Add a lunch break, an overnight shift that crosses midnight, or a payroll system that wants decimal hours, and a simple timesheet turns into a small math problem. This guide walks through every case with worked examples, a conversion table, and the overtime rules that decide what you actually get paid.

The short answer

To find hours worked, convert both the start time and the end time into a running total, subtract, then handle the minutes separately from the hours. A shift from 8:15 AM to 5:30 PM is 9 hours and 15 minutes, which equals 9.25 decimal hours. Subtract any unpaid break before you convert to decimal, and your payroll number is done.

Step 1: Convert clock times to a total

The core method is to work out the whole hours and the leftover minutes on their own, so the base-60 problem never bites you. Line up the start and end times and subtract each part:

hours worked = (end hour − start hour) with minutes adjusted

Take a shift from 8:15 to 17:30 (5:30 PM on a 24-hour clock). The hours go from 8 to 17, which is 9 hours. The minutes go from 15 to 30, which is 15 more minutes. So the answer is 9 hours 15 minutes. When the end minutes are smaller than the start minutes, borrow one hour worth of 60 minutes. For a 9:45 to 4:20 PM shift (16:20), you cannot take 45 from 20, so borrow: 16:20 becomes 15 hours and 80 minutes. 15 − 9 = 6 hours and 80 − 45 = 35 minutes, giving 6 hours 35 minutes.

Step 2: Subtract the lunch break

Most unpaid breaks are not part of paid hours, so you subtract them from the total. Work out the gross shift length first, then take off the break in minutes.

Say someone clocks in at 8:00 AM and out at 4:30 PM with a 30-minute unpaid lunch. Gross time is 8 hours 30 minutes. Subtract 30 minutes and you get exactly 8 hours 0 minutes of paid time. If the break were a full hour, paid time would be 7 hours 30 minutes.

A cleaner approach for longer or multiple breaks is to convert everything to total minutes, subtract, then convert back. For the 8:00 to 16:30 example: start is 8 × 60 = 480 minutes, end is 16 × 60 + 30 = 990 minutes. The gross is 990 − 480 = 510 minutes. Take off the 30-minute break to get 480 minutes, and 480 ÷ 60 = 8 hours.

Step 3: Handle overnight shifts across midnight

When a shift ends on the next calendar day, the end time reads as a smaller number than the start, so a plain subtraction gives a negative or nonsense result. The fix is to add 24 hours to the end time before subtracting.

A security guard works 10:00 PM to 6:00 AM. In 24-hour terms that is 22:00 to 6:00. Because 6 is less than 22, add 24 to the end: 6 + 24 = 30:00. Now subtract: 30:00 − 22:00 = 8 hours. The same trick works with minutes. A shift from 11:45 PM to 7:15 AM becomes 23:45 to 31:15, and 31:15 − 23:45 = 7 hours 30 minutes after borrowing.

Step 4: Convert hours and minutes to decimal hours

Payroll runs on decimal hours, not hours and minutes, because you multiply decimal hours by the pay rate to get gross pay. To convert, divide the minutes by 60:

decimal hours = whole hours + (minutes ÷ 60)

For 9 hours 15 minutes: 15 ÷ 60 = 0.25, so the answer is 9.25 hours. The quarter-hour marks are worth memorizing because they cover most real timesheets: 15 minutes is 0.25, 30 minutes is 0.5, and 45 minutes is 0.75. Anything else you divide by 60. At $20 an hour, 9.25 hours is 9.25 × 20 = $185 of gross pay.

Minutes-to-decimal conversion table

Keep this table next to your timesheet. It shows how common minute values map to decimal hours, both at the exact quarter marks and for a few in-between values you will hit often.

Notice that 10 minutes is 0.17, not 0.10. This is the classic trap: minutes are not the same as the decimal digits. Ten minutes is a sixth of an hour, so 10 ÷ 60 = 0.1667, which rounds to 0.17.

A full weekly timesheet example

Here is a realistic week for an hourly employee with a 30-minute unpaid lunch each day. Work out each day, then total the decimal hours for the week.

• Monday: 8:00 AM to 4:30 PM, minus 30 min lunch = 8.00 hours
• Tuesday: 8:15 AM to 5:30 PM, minus 30 min lunch = 8.75 hours
• Wednesday: 9:00 AM to 5:00 PM, minus 30 min lunch = 7.50 hours
• Thursday: 8:00 AM to 6:00 PM, minus 30 min lunch = 9.50 hours
• Friday: 8:00 AM to 4:45 PM, minus 30 min lunch = 8.25 hours

Add the daily decimals: 8.00 + 8.75 + 7.50 + 9.50 + 8.25 = 42.00 hours for the week. At $22 an hour, the straight-time value is 42 × 22 = $924 before we account for overtime, which we handle next.

Overtime basics

In the United States, the federal Fair Labor Standards Act (FLSA) requires non-exempt employees to be paid overtime at 1.5 times their regular rate for hours worked beyond 40 in a workweek. Overtime under the federal rule is based on the total for the week, not per day.

Our example week was 42.00 hours, so 40 hours are straight time and 2 hours are overtime. At a $22 base rate, overtime pays 22 × 1.5 = $33 per hour. Gross pay is (40 × 22) + (2 × 33) = 880 + 66 = $946.

Rounding rules to know

Many employers round clock punches to the nearest quarter hour. Under FLSA guidance, rounding is allowed as long as it does not consistently favor the employer over time. The most common method is the 7-minute rule: punches within 7 minutes of a quarter-hour mark round down, and punches at 8 minutes or more round up.

• Clock in at 8:07 rounds back to 8:00 (7 minutes or less)
• Clock in at 8:08 rounds forward to 8:15 (8 minutes or more)
• Clock out at 4:52 rounds back to 4:45
• Clock out at 4:53 rounds forward to 5:00

If your workplace does not round, use the exact punch times and divide the leftover minutes by 60 as shown above. Exact times are always the safest record to keep.

Common questions

How do I calculate hours worked with a lunch break?

Work out the full shift length from clock-in to clock-out first, then subtract the unpaid break in minutes. For an 8:00 AM to 4:30 PM shift with a 30-minute lunch, the gross is 8 hours 30 minutes, and after the break you have 8 hours 0 minutes of paid time. Paid breaks are not subtracted, so check your policy on which breaks count.

How do I convert minutes to decimal for payroll?

Divide the minutes by 60 and add the result to the whole hours. So 15 minutes is 0.25, 30 minutes is 0.5, and 45 minutes is 0.75. For a value like 20 minutes, 20 ÷ 60 = 0.33. Multiply the decimal hours by your pay rate to get gross pay for that shift.

How do I calculate hours across midnight?

Add 24 hours to the end time before you subtract. A shift from 10:00 PM to 6:00 AM is 22:00 to 6:00 in 24-hour format. Since 6 is smaller than 22, use 6 + 24 = 30, then 30 − 22 = 8 hours. Borrow for the minutes the same way you would in any subtraction.

Is a 15-minute break paid or unpaid?

Under federal rules, short rest breaks of 5 to 20 minutes are generally counted as paid work time, so you do not subtract them. Meal periods of 30 minutes or more are usually unpaid and are subtracted, provided the employee is fully relieved of duties. State rules vary, so confirm with your employer.

What is 7 hours and 45 minutes in decimal?

It is 7.75 hours, because 45 ÷ 60 = 0.75. Likewise 7 hours 30 minutes is 7.5, and 7 hours 15 minutes is 7.25. Once the quarter marks are second nature, most timesheet conversions take a few seconds.