How to Calculate Work Hours
Calculating hours worked is simple arithmetic — but the clock runs on base-60 while payroll math runs on base-10, and that mismatch trips people up. The formula is:
Hours Worked = (Clock Out − Clock In) − Unpaid Break
Example: clock in at 8:45 AM, out at 5:15 PM, with a 45-minute unpaid lunch. That's 8.5 hours minus 0.75 hours = 7.75 hours worked.
The part people get wrong is converting minutes to decimal hours. Thirty minutes is 0.5 hours — writing 0.30 instead would understate the time by 40%. Divide minutes by 60 to convert:
| Minutes | Decimal Hours | Minutes | Decimal Hours |
|---|---|---|---|
| 15 min | 0.25 h | 45 min | 0.75 h |
| 20 min | 0.33 h | 48 min | 0.80 h |
| 30 min | 0.50 h | 54 min | 0.90 h |
| 40 min | 0.67 h | 60 min | 1.00 h |
This calculator does the decimal conversion automatically, showing both formats (e.g. 8h 45m = 8.75 h).
Overtime Rules in the US
Under the Fair Labor Standards Act (FLSA), non-exempt hourly workers must be paid 1.5× their regular rate for every hour over 40 in a single workweek. The 40-hour threshold resets each workweek — it cannot be averaged across a bi-weekly or monthly pay period (U.S. Department of Labor).
Some states impose stricter daily rules. California, for example, requires 1.5× after 8 hours in a single day and 2× (double time) after 12 hours. Other states with daily overtime rules include Alaska, Colorado, and Nevada — check your state's labor department for specifics.
Worked example: a warehouse associate works 44 hours in a week at $16.50/hour.
- Regular pay: 40 × $16.50 = $660
- Overtime: 4 hours × ($16.50 × 1.5 = $24.75) = $99
- Gross pay: $759
Note: employers generally can't substitute time off for cash overtime. If your company "banks" extra hours toward future comp time instead of paying 1.5×, that's usually a violation — with limited exceptions for government employers.
Do Breaks Count as Work Time?
It depends on the type of break:
- Paid short breaks (under 20 minutes) — count as work time under federal rules. A coffee run or quick smoke break is paid.
- Meal breaks (30 minutes or more) — may be unpaid, but only if you are completely relieved of duties. If you're on call or working through lunch, it should count.
- Auto-deducted breaks you didn't actually take — this can be wage theft. Keep your own records of actual break times.
In the calculator, enter only unpaid break minutes. If your break is paid, leave it at 0.
Overnight & Cross-Midnight Shifts
Shifts that cross midnight — 10:00 PM to 6:00 AM — confuse manual calculators. The fix is simple: add 24 hours to the clock-out time.
10:00 PM → 6:00 AM: (6 + 24) − 22 = 8.0 hours worked (minus break).
This calculator detects overnight shifts automatically: if your clock-out time is earlier than your clock-in time, it assumes the shift crossed midnight.
Common Mistakes When Calculating Hours
- Treating time as base-10 — 45 minutes is 0.75 hours, not 0.45. Always divide minutes by 60.
- Forgetting unpaid breaks — a 30-minute lunch every day is 2.5 unpaid hours per week, which adds up fast.
- Averaging overtime across pay periods — two 45-hour weeks in a bi-weekly pay period still earn 10 overtime hours. FLSA never averages.
- Using clock-out minus clock-in for overnight shifts — you'll be off by 12 hours without the +24 adjustment.
- Ignoring state daily overtime — federal rules are a floor, not a ceiling. If you work in California, daily OT rules apply even if you're under 40 hours that week.
Frequently Asked Questions
How do I calculate hours worked?
Take the difference between clock-out and clock-in, then subtract any unpaid break. Example: 8:45 AM to 5:15 PM with a 45-minute lunch = 7.75 hours worked.
How is overtime calculated?
Under FLSA, hours beyond 40 in a workweek are paid at 1.5× your regular rate. Some states (California, Alaska, Colorado, Nevada) add daily rules — 1.5× after 8 hours in a day, and up to 2× after 12 hours.
Do lunch breaks count as work hours?
Short breaks under 20 minutes are paid and count as work time. Meal breaks of 30+ minutes can be unpaid only if you're completely relieved of duties — being on call doesn't qualify. Enter only unpaid break minutes in the calculator.
How do I calculate an overnight shift?
Add 24 hours to the clock-out time: a 10:00 PM to 6:00 AM shift is (6 + 24) − 22 = 8.0 hours (minus break). The calculator detects this automatically when clock-out is earlier than clock-in.
What is 8.75 hours in hh:mm?
8.75 decimal hours = 8 hours and 45 minutes. Multiply the decimal part by 60: 0.75 × 60 = 45 minutes.
Does overtime reset every week?
Yes. FLSA overtime is calculated per workweek — a fixed 168-hour period your employer defines (often Sunday–Saturday). Hours cannot be averaged across a two-week pay period: two 45-hour weeks still produce 10 overtime hours, even on one bi-weekly paycheck. Bi-weekly is the most common US pay schedule, so this trips up many workers.
Methodology: Calculations follow US federal FLSA overtime rules (40-hour workweek, 1.5× rate) with an optional daily-overtime mode for states like California. Figures are gross pay estimates before taxes — state wage laws vary and this tool does not constitute legal or payroll advice.