How to Calculate Hours Worked (Step by Step)
By Atharv · Updated July 19, 2026
Calculating hours worked sounds trivial until you actually try it: clocks run in 60s, payroll runs in 100s, lunch has to come out in the middle, and some shifts cross midnight. This guide walks through the exact method, by hand, with real numbers. (If you just want the answer, our free time card calculator does all of this automatically.)
Step 1: Subtract the start time from the end time
The easiest way to avoid AM/PM mistakes is to convert both times to 24-hour format first (2:30 PM = 14:30; see our military time converter if you need a refresher). Then subtract hours and minutes separately.
Example: 8:30 AM to 5:15 PM
5:15 PM = 17:15. Then 17:15 − 8:30 = 8 hours 45 minutes.
(If the minutes won’t subtract, say :15 minus :30, borrow an hour: 17:15 becomes 16:75, and 16:75 − 8:30 = 8:45.)
Step 2: Deduct unpaid breaks
Subtract any unpaid time, usually lunch. Paid breaks (many 10–15 minute rest breaks are paid) stay in the total, so check which kind your employer uses.
Continuing: 8 h 45 m − 45-minute lunch
8:45 − 0:45 = 8 hours 0 minutes worked.
Step 3: Convert minutes to decimal hours
Payroll systems multiply hours by a pay rate, so minutes must become decimals: divide the minutes by 60. Fifteen minutes is 0.25, half an hour is 0.50, and 45 minutes is 0.75.
| Minutes | Decimal | Minutes | Decimal |
|---|---|---|---|
| 6 | 0.10 | 36 | 0.60 |
| 12 | 0.20 | 42 | 0.70 |
| 15 | 0.25 | 45 | 0.75 |
| 20 | 0.33 | 48 | 0.80 |
| 30 | 0.50 | 54 | 0.90 |
The full 1–60 minute table is on our time to decimal calculator page.
Step 4: Add up the week
Repeat for each day and sum the decimals. A realistic week might look like this:
| Day | Shift | Break | Hours |
|---|---|---|---|
| Monday | 8:30 AM – 5:15 PM | 0:45 | 8.00 |
| Tuesday | 9:00 AM – 5:30 PM | 0:30 | 8.00 |
| Wednesday | 8:45 AM – 4:55 PM | 1:00 | 7.17 |
| Thursday | 9:00 AM – 6:20 PM | 0:45 | 8.58 |
| Friday | 8:00 AM – 2:00 PM | - | 6.00 |
| Weekly total | 37.75 | ||
Special case: overnight shifts
When a shift crosses midnight, the end time is “earlier” than the start time, so add 24 hours to the end before subtracting. A 10:00 PM to 6:00 AM shift is (6:00 + 24:00) − 22:00 = 8 hours. Our calculator handles this automatically, as does the time duration calculator for one-off checks.
A note on time clock rounding
Many employers round punches to the nearest 5, 6, or 15 minutes, and rounding is generally expected to be even-handed: it can’t always round in the employer’s favor. Under the common quarter-hour method, clocking in at 8:53 counts as 9:00, while 8:52 counts as 8:45. If your employer rounds, our calculator has a matching “Round Daily Totals” option so your numbers line up with payroll’s.
Common mistakes
- Treating 7:30 as 7.30 hours. It’s 7.50. Minutes are sixtieths, not hundredths.
- Forgetting to subtract unpaid lunch, or subtracting paid breaks.
- AM/PM mix-ups on afternoon start times (work in 24-hour format).
- Reconstructing the week from memory on Friday. Record times daily.
Skip the math
Everything above, including breaks, overnight shifts, rounding, weekly overtime, and pay, is automated in the free time card calculator. Enter your times and download a finished PDF timesheet. If you track hours on paper first, grab a free printable timesheet template.