How to calculate hours worked from a timesheet
How to turn clock-in and clock-out times into paid hours, why decimal hours trip people up, how to handle overnight shifts, and where the money quietly leaks.
2 min read
Short answer: find the gap between clock-in and clock-out, subtract any unpaid break, then convert to decimal hours for payroll (30 minutes is 0.5, not 0.30). For overnight shifts, where clock-out is earlier than clock-in, add 24 hours first.
Step by step
Take a 09:00 to 17:30 shift with a 30-minute unpaid lunch:
- Find the span. 09:00 to 17:30 is 8 hours 30 minutes.
- Subtract unpaid breaks. Take off 30 minutes → 8 hours 0 minutes of paid time.
- Convert to decimal. 8 hours = 8.00. Multiply by the hourly rate for pay.
Our timesheet calculator does all three steps, including the pay, in one go.
Decimal hours are where mistakes happen
Payroll multiplies decimal hours by the rate, and minutes are not decimals. The conversions worth memorising:
| Minutes | Decimal |
|---|---|
| 15 min | 0.25 |
| 20 min | 0.33 |
| 30 min | 0.50 |
| 45 min | 0.75 |
The classic error is treating “8.30” (meaning 8 hours 30 minutes) as 8.30 in decimal. That’s an 18-minute difference per shift — small once, real over a year across a team.
Overnight shifts
When the clock-out time is earlier than the clock-in — say 22:00 to 06:00 — the shift has crossed midnight. Add 24 hours before subtracting, so 06:00 becomes 30:00: that’s an 8-hour shift before breaks, not minus-16. The calculator detects this automatically; by hand, it’s an easy one to fluff.
Where the money leaks
Adding up paper or spreadsheet timesheets is slow and it leaks money in three predictable ways:
- Generous rounding. “Started about nine” becomes 09:00 on the dot, every time, in the employee’s favour.
- Forgotten breaks. An unpaid 30 left in the total is 30 minutes paid for nothing.
- Buddy-punching. Someone clocking a colleague in inflates hours that never happened — see how to stop buddy-punching.
The faster way
WagePilot skips the maths entirely: staff clock in and out on their phone with a geofence or QR check, the app subtracts breaks and totals the approved hours, and you export them straight to payroll. No sheet to add up, no rounding to argue about, and a tamper-evident record if HMRC ever asks — which ties into how long you must keep those records.
This guide is general information, not legal advice. Check GOV.UK or a qualified adviser for your situation. WagePilot handles the tracking automatically, but you remain responsible for your own compliance.