The Basic Calculation
Total hours worked = End time − Start time − Break time
If you clock in at 8:30 AM and clock out at 5:15 PM with a 45-minute lunch break:
5:15 PM − 8:30 AM = 8 hours 45 minutes − 45 minutes = 8 hours
That is the simple case. Real-world hour calculations involve overtime thresholds, multiple shifts, rounding rules, and the question of how to handle partial hours.
Converting to Decimal Hours
Payroll systems typically use decimal hours rather than hours and minutes. A timesheet entry of 8 hours 15 minutes becomes 8.25 hours for pay calculation.
Quick conversions:
- 15 minutes = 0.25 hours
- 30 minutes = 0.50 hours
- 45 minutes = 0.75 hours
For other values: divide minutes by 60. 22 minutes = 22 ÷ 60 = 0.37 hours (rounded to two decimal places).
Handling Overnight Shifts
If you start at 10:00 PM and finish at 6:30 AM, a simple subtraction gives a negative number. The correct calculation crosses midnight:
From 10:00 PM to midnight = 2 hours
From midnight to 6:30 AM = 6.5 hours
Total = 8.5 hours
Alternatively: convert to 24-hour format (22:00 to 06:30), add 24 to the end time if it is smaller (06:30 + 24:00 = 30:30), then subtract (30:30 − 22:00 = 8:30, or 8.5 hours).
Rounding Rules
Many employers round clock-in and clock-out times to the nearest increment. Common rounding increments:
6-minute rounding (1/10 hour):
- 8:01–8:03 rounds to 8:00
- 8:04–8:09 rounds to 8:06
- 8:10–8:15 rounds to 8:12
15-minute rounding (1/4 hour):
- 8:01–8:07 rounds to 8:00
- 8:08–8:22 rounds to 8:15
- 8:23–8:37 rounds to 8:30
US labor law (FLSA) allows rounding as long as it averages out fairly over time — rounding must not systematically favor the employer.
Overtime Calculation
US federal law requires overtime pay (1.5× the regular rate) for hours worked beyond 40 in a workweek. Some states have daily overtime thresholds (California requires overtime after 8 hours in a day).
Weekly overtime example:
- Mon–Fri: 9 hours per day = 45 hours total
- Regular hours: 40 × $20 = $800
- Overtime hours: 5 × $30 = $150
- Total: $950
Multiple Shifts in One Day
Some time card systems require calculating hours for multiple clock-in/clock-out pairs in a single day:
- Shift 1: 7:00 AM – 11:30 AM = 4.5 hours
- Shift 2: 12:15 PM – 5:00 PM = 4.75 hours
- Total: 9.25 hours
The break between shifts (11:30 AM to 12:15 PM) is unpaid and automatically excluded because it falls between clock-out and clock-in.
How to Use the Toobits Hours Calculator
Enter your start time and end time, and optionally subtract break time. The calculator shows total hours in both time format (hours:minutes) and decimal format for payroll. Calculate daily hours or add up an entire week. Everything runs in your browser — no data is stored or sent anywhere.