Whether you run payroll, bill a client or just check your own week, you need the same thing: the exact number of hours worked. The math is simple, but breaks, minutes and night shifts trip people up. Here’s the method, with examples you can copy.
The basic formula
Hours worked = end time − start time − unpaid breaks
Example: start 08:15, end 16:45, 30-minute unpaid lunch.
- 16:45 − 08:15 = 8 hours 30 minutes
- 8:30 − 0:30 break = 8 hours 0 minutes
Tip: convert both times to the 24-hour clock first. “4:45” in the afternoon is 16:45 — mixing AM and PM is the most common mistake.
Convert minutes to decimal hours
Payroll and invoices use decimal hours: 7 hours 45 minutes is 7.75 hours, not 7.45. Divide the 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 |
Example: 7 h 45 min × €20 per hour = 7.75 × 20 = €155. Writing it as 7.45 would cost the employee €6.
Shifts that cross midnight
If the shift ends after midnight, add 24 hours to the end time before subtracting.
Example: start 22:00, end 06:30, 30-minute break → (06:30 + 24:00) − 22:00 = 8:30, minus 0:30 = 8 hours.
Weekly total and overtime
Add up each day in decimals, then compare with the regular hours in the contract.
| Day | Start | End | Break | Hours |
|---|---|---|---|---|
| Mon | 08:00 | 16:30 | 0:30 | 8.00 |
| Tue | 08:00 | 17:15 | 0:30 | 8.75 |
| Wed | 08:00 | 16:30 | 0:30 | 8.00 |
| Thu | 08:00 | 18:00 | 0:30 | 9.50 |
| Fri | 08:00 | 16:00 | 0:30 | 7.50 |
| Total | 41.75 | |||
With a 40-hour week, that’s 1.75 hours of overtime. Whether overtime is counted per day or per week, and how it’s paid, depends on your contracts and local law — check them before you set up a spreadsheet formula.
Rounding
Some companies round clock times to the nearest 5, 10 or 15 minutes. If you do, round the same way in both directions and write the rule down. Rounding only in the company’s favour is not allowed in many countries. Simplest option: don’t round — let software record the exact minute.
Common mistakes
- Treating minutes as decimals (7:45 written as 7.45).
- Forgetting the unpaid break — or subtracting a paid one.
- Negative results on night shifts (missing the +24 h).
- Adding hours and minutes separately and forgetting to carry over 60 minutes.
- Different people using different rules for the same team.
Let the app do the math
Doing this by hand for one person is fine. For a team, every week, it’s where errors and arguments start. In Clocknico:
- Employees clock in and out with a QR code at the door, or from the app when working remotely — the exact minute is recorded.
- Hours are totalled per day, week and month, and per working time (for example Office, Field and Overtime).
- Shifts past midnight and manual corrections are handled automatically.
- The payroll CSV gives decimal hours per person, ready for your accountant — see monthly hours report for payroll.
Clocknico is free for teams of up to 5 users. Create a free company account.