What this calculator does and when to use it
This calculator turns a start time, end time, and unpaid break length into your net hours worked per shift, then extrapolates that to weekly, monthly, and annual totals — while separating regular hours from overtime hours based on a daily threshold you set. It also handles overnight shifts automatically: if the end time is earlier than the start time (like 22:00 to 06:00), it assumes the shift crosses midnight and adds 24 hours before subtracting breaks.
Use it to double-check a paycheck against your actual schedule, to plan how many hours a new part-time or shift-work schedule will add up to per month, or to see how much of your week counts as overtime under a given daily threshold (commonly 8 hours/day in many U.S. workplaces, though this varies by employer and jurisdiction).
The method
- Shift length = End time − Start time (in minutes), adding 24 hours if the result is zero or negative to support overnight shifts.
- Net hours worked = (Shift length − Break duration) ÷ 60.
- Daily regular hours = the smaller of net hours worked and your overtime threshold; daily overtime = anything above that threshold.
- Weekly, monthly, and annual totals extrapolate daily hours using your days-per-week and weeks-per-year inputs, with monthly hours averaged as weekly hours × (weeks per year ÷ 12).
Worked example
Suppose you work 8:00 AM to 6:00 PM (a 600-minute shift) with a 30-minute break, 5 days a week, 50 weeks a year, and an 8-hour/day overtime threshold. Net hours = (600 − 30) ÷ 60 = 9.5 hours/day. Since 9.5 exceeds the 8-hour threshold, that splits into 8.0 regular hours and 1.5 overtime hours per day. Weekly total = 9.5 × 5 = 47.5 hours (40 regular + 7.5 overtime). Monthly average = 47.5 × (50 ÷ 12) ≈ 197.92 hours, and annual total = 47.5 × 50 = 2,375 hours — matching exactly what the calculator returns for these inputs.
Common mistakes and how to interpret the result
- Forgetting to subtract unpaid breaks. Only unpaid break time should go in the break field — paid breaks are typically still counted as worked hours by employers, so including them would understate your hours.
- Using the wrong overtime threshold for your situation. Overtime rules vary — some employers calculate overtime weekly (over 40 hours) rather than daily; this calculator's daily-threshold model won't match a weekly-overtime policy, so treat the overtime split as an estimate to verify against your employer's actual policy.
- Assuming every week matches your "weeks per year" input exactly. The monthly and annual figures assume a consistent schedule with no unpaid time off beyond what you've already excluded via weeks-per-year — actual pay stubs will differ around holidays, sick days, or vacation.
- Entering overnight shifts incorrectly. If your end time is earlier than your start time (e.g., 22:00 to 06:00), the calculator automatically treats it as crossing midnight — you don't need to manually add 24 hours.