How to Calculate Time Card Hours (With Examples & Free Calculator)
Time card math looks simple until 8:47 AM meets 5:23 PM with a 35-minute lunch. The mistakes are always the same: mixing up minutes with decimals, forgetting unpaid breaks, and mangling overnight shifts. Here's the by-hand method payroll clerks use — and if you'd rather skip the arithmetic, our free time card calculator does every step below automatically.
Step 1: Convert clock times to 24-hour format
Working in AM/PM invites errors. Convert every punch to 24-hour time first: 8:47 AM stays 8:47, and 5:23 PM becomes 17:23 (add 12 to any PM hour except 12 PM). Now subtraction works normally.
Step 2: Subtract clock-in from clock-out
17:23 − 8:47: you can't take 47 from 23, so borrow an hour — 16:83 − 8:47 = 8 hours 36 minutes. For overnight shifts where the out-time is "earlier" than the in-time (22:00 → 6:00), add 24 hours to the out-time first: 30:00 − 22:00 = 8 hours.
Step 3: Deduct unpaid breaks
Subtract unpaid break minutes from each day. 8h 36m minus a 35-minute lunch = 8h 01m. Note that paid breaks (many states require paid rest breaks under 20 minutes) stay in the total — only deduct breaks your employer doesn't pay for.
Step 4: Convert minutes to decimal hours
Payroll systems multiply decimal hours by your rate. Divide the minutes by 60: 8h 01m = 8.02 hours. The classic error is writing 8h 30m as "8.3" — it's 8.5. Common conversions: 15 min = 0.25 · 20 min = 0.33 · 30 min = 0.5 · 45 min = 0.75.
Step 5: Total the week and split out overtime
Add the daily decimals. Under the US FLSA, hours over 40 in a workweek are overtime at 1.5× for non-exempt employees. A 46.25-hour week at $18/hour = 40 × $18 + 6.25 × $27 = $720 + $168.75 = $888.75 gross. Price the overtime piece precisely with the overtime calculator.
Worked example: a full week
| Day | In | Out | Break | Hours |
|---|---|---|---|---|
| Mon | 8:00 | 17:00 | 60 min | 8.00 |
| Tue | 8:47 | 17:23 | 35 min | 8.02 |
| Wed | 8:00 | 18:30 | 30 min | 10.00 |
| Thu | 8:00 | 17:00 | 60 min | 8.00 |
| Fri | 8:00 | 17:15 | 45 min | 8.50 |
| Total | 42.52 hrs → 40 regular + 2.52 OT | 42.52 | ||
At $18/hour that's 40 × $18 + 2.52 × $27 = $720 + $68.04 = $788.04 gross. Want the annual picture? Convert your average week with the hourly to salary calculator.
Rounding rules employers use
US employers may round punches to the nearest 5, 6, or 15 minutes — but rounding must be neutral over time, not always in the employer's favor (29 CFR § 785.48). If your 8:58 punch-in always becomes 9:00 but your 5:02 punch-out becomes 5:00, that pattern is worth questioning.