How to calculate hours worked, with breaks and decimals
Calculating hours worked is subtraction with a few traps in it: the unpaid lunch, the shift that crosses midnight, and the minutes that must become decimals before payroll accepts them. This guide takes each step with real numbers, so you can check a timesheet by hand or see what the work hours calculator is doing with your week.
The basic sum: finish minus start, minus unpaid breaks
For one shift, take the start time away from the finish time, then take off any break that is not paid. A day from 9:00 to 17:30 is 8 hours 30 minutes on the clock. With a 30 minute unpaid lunch, the hours worked are 8 hours exactly.
When the minutes do not line up, borrow an hour: 16:20 is 15 hours and 80 minutes, so 15:80 minus 8:45 is 7 hours 35 minutes, and 7 hours 5 minutes after a 30 minute break. Write both times in 24 hour form first, so 4:20 pm cannot be mistaken for 4:20.
Only unpaid breaks come off. A paid 15 minute rest break is part of the shift and stays in the total; an unpaid meal break comes out. If your contract does not say which kind a break is, ask before building a timesheet around a guess, because subtracting a paid break short-changes you every day.
Overnight shifts: a finish earlier than the start means the next day
A night shift from 22:00 to 06:00 looks like minus 16 hours if you subtract blindly. The finish belongs to the next day, so add 24 hours to it first: 30:00 minus 22:00 is 8 hours. A shift from 23:00 to 07:30 with a 30 minute unpaid break is 8 hours worked. The calculator applies this rule on its own: whenever the finish is earlier than the start, it treats the finish as the following day.
Converting minutes to decimal hours
Payroll systems multiply hours by a rate, so they want 8.25, not 8:15. Divide the minutes by 60 and add the result to the whole hours: 15 divided by 60 is 0.25, so 8 hours 15 minutes is 8.25 hours, and 50 divided by 60 is 0.8333, which rounds to 0.83.
| Minutes | Decimal hours | Exact value |
|---|---|---|
| 5 | 0.08 | 0.0833 |
| 10 | 0.17 | 0.1667 |
| 15 | 0.25 | 0.25 |
| 20 | 0.33 | 0.3333 |
| 30 | 0.50 | 0.5 |
| 40 | 0.67 | 0.6667 |
| 45 | 0.75 | 0.75 |
| 50 | 0.83 | 0.8333 |
Two decimal places are enough for pay, though they lose a fraction of a minute: 0.33 hours is 19.8 minutes, not 20. That is why the calculator keeps exact minutes and shows the decimal form alongside them.
Hours and minutes or decimal hours on the payslip
A timesheet in hours and minutes is easy to check against a clock; a payslip in decimal hours is easy to multiply. Mixing them up is the commonest timesheet error there is: 8.30 hours is 8 hours 18 minutes, not 8 hours 30 minutes. If a form does not say which it wants, ask, and write 8.5 rather than 8.50 so nobody reads it as a time.
Adding a week of hours worked
Add the days in hours and minutes first, then convert the total once. Here is a week with a 30 minute unpaid lunch every day:
| Day | Start | Finish | On the clock | Hours worked | Decimal |
|---|---|---|---|---|---|
| Monday | 8:30 | 17:15 | 8:45 | 8:15 | 8.25 |
| Tuesday | 9:00 | 17:30 | 8:30 | 8:00 | 8.00 |
| Wednesday | 8:45 | 18:05 | 9:20 | 8:50 | 8.83 |
| Thursday | 9:10 | 16:40 | 7:30 | 7:00 | 7.00 |
| Friday | 9:00 | 14:00 | 5:00 | 4:30 | 4.50 |
The hours add to 35 and the minutes to 95, which is 1 hour 35 minutes, so the week is 36 hours 35 minutes. In decimals, 35 divided by 60 is 0.5833, so 36.58 hours. Adding the rounded daily decimals happens to give 36.58 too, but when the two disagree the converted exact total is the right one. The same five days in the work hours calculator show 36:35 with the decimal beneath, and an hourly rate turns it into gross pay.
Rounding to the nearest quarter hour
Some employers record times to the nearest 5, 6 or 15 minutes rather than the exact minute. In the United States, 29 CFR 785.48 describes the practice of recording starting and stopping times to the nearest 5 minutes, or the nearest one-tenth or quarter of an hour, and says it will be accepted for enforcement purposes provided it does not, over a period of time, fail to compensate employees for all the time they have actually worked. Rounding has to be neutral, in other words; it cannot always land in the employer's favour.
In practice: clocking in at 8:56 rounds to 9:00 and out at 17:06 rounds to 17:00, so 8 hours 10 minutes becomes 8 hours. The next day, 9:04 rounds to 9:00 and 17:10 to 17:15, so 8 hours 6 minutes becomes 8 hours 15 minutes: one day loses 10 minutes, the next gains 9. Outside the US the rules depend on your country and contract, so check before adopting rounding at all.
Biweekly pay periods: one week at a time
If you are paid every two weeks, add each week up on its own. Weekly overtime rules, where they apply, are set per workweek, so 44 hours in week one and 36 in week two is not the same as two weeks of 40. The overtime pay guide works through that case. The calculator handles one week at a time for the same reason: run it twice and add the totals.
Common mistakes
- Subtracting a paid break. A paid rest break taken out of every shift costs 15 minutes a day, more than an hour a week.
- Forgetting the day change. A night shift entered as same-day times gives a negative answer. Treat the finish as the next day.
- Mixing minutes and decimals. 7.45 hours is 7 hours 27 minutes.
- Rounding before adding. Sum the exact minutes for the week, then convert once.
Keep the raw start, finish and break for every day, not just the total, so a query months later can be answered. The work hours calculator keeps all three for each day, and its share link carries them in the part of the address after the #, which never reaches a server.
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