To calculate hours worked: subtract the start time from the end time, subtract unpaid breaks, convert the remaining minutes to decimal hours (minutes ÷ 60), and add the days together per workweek. That single sentence is the whole method — the rest of this guide makes each step foolproof.
Step 1 — Find each day’s span
Write down the clock-in and clock-out time, then subtract. The easiest mental model is converting both times to minutes since midnight:
| Time | Minutes since midnight |
|---|---|
| 8:30 AM | 510 |
| 5:15 PM | 1,035 |
1,035 − 510 = 525 minutes = 8 hours 45 minutes. For overnight shifts the end lands “before” the start — add 24 hours: 10:00 PM (1,320) to 6:00 AM (360 + 1,440 = 1,800) is 480 minutes = 8 hours.
Step 2 — Deduct unpaid breaks only
Not every break leaves your paycheck:
- Unpaid meal periods — typically 30+ minutes, fully relieved of duty — are deducted.
- Short rest breaks of 5–20 minutes are paid time under the FLSA and stay in your hours.
- Working lunches count as work. If you covered the phones while eating, that lunch is paid time.
So an 8:30 AM–5:15 PM day with a 45-minute unpaid lunch is 8:45 − 0:45 = 8 hours.
Step 3 — Convert minutes to decimal hours
Payroll multiplies decimal hours by your rate. Divide minutes by 60:
| h:mm | Decimal |
|---|---|
| 8:15 | 8.25 |
| 8:20 | 8.33 |
| 8:30 | 8.50 |
| 8:45 | 8.75 |
The classic mistake is writing 8 hours 30 minutes as “8.30” — that’s 8 hours 18 minutes in decimal. The decimal hours calculator has the full 1–60 minute chart.
Step 4 — Total the workweek and split overtime
Add the daily figures inside each workweek (a fixed 7-day cycle your employer defines). Hours over 40 in that week are overtime at 1.5× under federal law; California and a few other states add daily thresholds — over 8 hours in a day in California earns overtime even in a short week. Overtime never averages across weeks, even on biweekly pay.
Full worked example
A warehouse associate, Monday–Friday, 7:00 AM–3:45 PM with a 30-minute unpaid lunch, plus a 6-hour Saturday:
| Day | Span | Lunch | Paid hours |
|---|---|---|---|
| Mon–Fri (each) | 8:45 | 0:30 | 8:15 (8.25) |
| Saturday | 6:00 | — | 6:00 (6.00) |
| Week total | 47:15 (47.25) |
Overtime split: 40 regular + 7.25 OT. At $17/hour: 40 × $17 + 7.25 × $25.50 = $680 + $184.88 = $864.88 gross.
The time card calculator runs this whole pipeline — spans, breaks, decimals, state overtime — as you type, and exports the result for payroll.
Avoid the three classic errors
- Treating minutes as decimals (8:30 ≠ 8.30 hours).
- Deducting paid rest breaks — only bona fide meal periods come out.
- Averaging two weeks to dodge overtime — each workweek stands alone.