How to use this calculator
Enter two durations in hours and minutes. Choose Add or Subtract. Subtraction takes the second duration away from the first and can produce a negative result.
The math behind it
Seconds = hours × 3,600 + minutes × 60 Combined duration = first duration ± second duration Decimal hours = combined seconds ÷ 3,600
A worked example
1 hour 45 minutes + 30 minutes = 2 hours 15 minutes, or 2.25 decimal hours.
Assumptions & precision
This tool compares durations, not clock times or calendar dates. It does not apply time zones, daylight saving, payroll rounding, or unpaid breaks. Hours must be whole numbers from 0 to 1,000,000; minutes may be decimal values from 0 up to (but not including) 60. Duration display rounds to the nearest second; decimal hours use the unrounded duration and show up to 6 decimal places.
A common question
Is 1 hour 30 minutes the same as 1.30 hours?
No. Thirty minutes is half an hour, so 1 hour 30 minutes equals 1.5 decimal hours.