Guide
How to Calculate Hours Worked
The full method, by hand — including the two places people most often go wrong: decimal conversion and overnight shifts.
The short version
- Convert every clock-in and clock-out time to the 24-hour clock so the subtraction is straightforward.
- Subtract the start time from the end time. If the end is earlier than the start, add 24 hours because the shift crossed midnight.
- Subtract any unpaid break minutes from that day’s total.
- Convert the remaining minutes to decimal hours by dividing by 60.
- Add the daily decimal totals together to get the weekly total.
- Apply the overtime threshold to each seven-day week separately, not to the pay period as a whole.
- Multiply regular hours by the hourly rate and overtime hours by 1.5 times the rate.
If you would rather not do it by hand, thetime card calculator runs every one of these steps as you type.
Step 1 — Use 24-hour time
AM/PM arithmetic is where mistakes creep in. Convert first: 1:00 PM is 13:00, 5:30 PM is 17:30, 12:00 AM is 00:00, and 12:00 PM is 12:00. Note that midnight and noon are the two that catch people out.
Step 2 — Subtract, and watch for midnight
A 09:00 to 17:30 shift is a plain subtraction: 17:30 − 09:00 = 8 hours 30 minutes.
When the clock-out is earlier than the clock-in, the shift crossed midnight. Add 24 hours to the end time before subtracting. A 22:00 to 06:00 shift becomes 30:00 − 22:00 = 8 hours. Subtracting directly would give you negative sixteen.
Step 3 — Take out the unpaid break
Deduct the unpaid meal period from the shift. A 9-hour shift with a 30-minute lunch leaves 8 hours 30 minutes of payable time. Short paid rest breaks stay in.
Step 4 — Convert to decimal hours
Payroll runs on decimals, so divide the leftover minutes by 60.
| Minutes | Decimal | Minutes | Decimal |
|---|---|---|---|
| 5 | 0.08 | 35 | 0.58 |
| 10 | 0.17 | 40 | 0.67 |
| 15 | 0.25 | 45 | 0.75 |
| 20 | 0.33 | 50 | 0.83 |
| 25 | 0.42 | 55 | 0.92 |
| 30 | 0.50 | 60 | 1.00 |
The classic error: writing 7 hours 45 minutes as 7.45. It is 7.75. Over a five-day week that single habit costs about an hour and a half.
Step 5 — Add up the week
Sum the daily decimals. Keep two decimal places throughout and round only at the end; rounding each day first compounds the error across the week.
Step 6 — Apply overtime per week
Overtime is assessed against a seven-day workweek, never against a pay period. On a biweekly card, score each week on its own. Fifty hours in week one and twenty in week two is ten hours of overtime, even though the 70-hour total sits below eighty.
Step 7 — Work out the pay
Regular hours times the rate, plus overtime hours times 1.5 times the rate, plus any double-time hours at twice the rate. At $20 an hour, 40 regular and 6 overtime hours is $800 + $180 = $980 gross.
A worked example
| Day | In | Out | Break | Hours |
|---|---|---|---|---|
| Mon | 08:00 | 17:00 | 30 | 8.50 |
| Tue | 08:00 | 18:30 | 30 | 10.00 |
| Wed | 08:00 | 16:45 | 30 | 8.25 |
| Thu | 08:00 | 17:00 | 30 | 8.50 |
| Fri | 22:00 | 06:00 | 30 | 7.50 |
| Total | 42.75 |
Under the weekly rule that is 40 regular hours and 2.75 overtime hours. At $20 an hour: $800 regular plus $82.50 overtime, for $882.50 gross. Friday is the overnight shift — 22:00 to 06:00 is 8 hours, less the 30-minute break.
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Frequently asked questions
How do I convert minutes to decimal hours?
Divide the minutes by 60. Fifteen minutes is 0.25, thirty is 0.5, forty-five is 0.75, and ten is roughly 0.17. The mistake to avoid is writing 7 hours 45 minutes as 7.45 — it is 7.75.
How do I calculate hours for an overnight shift?
Add 24 hours to the clock-out time before subtracting. A shift from 22:00 to 06:00 becomes 30:00 minus 22:00, which is 8 hours.
Do I round punch times before or after subtracting?
Before. Payroll practice is to round each punch to the nearest increment first, then take the difference. Rounding the resulting duration instead can shift a total by several minutes over a week.
What is the 7-minute rule?
With 15-minute rounding, punches within 7 minutes of a quarter hour round down and 8 minutes or more round up. It is lawful only when it works out neutrally over time — an employer may not round exclusively in its own favour.