Everyday
Time Duration Calculator
Add two durations expressed in hours and minutes, then convert the result to decimal hours and billable units. The calculator uses total minutes = hours × 60 + minutes. It returns more than one result so you can check the main answer against a useful secondary measure. Sixty minutes make one hour; decimal 1.50 hours means 1 hour 30 minutes, not 1 hour 50 minutes. This tool adds durations and does not handle calendar dates, daylight-saving changes, or time zones.
Check the displayed units, assumptions, and rounding before relying on the result.
Calculate and compare
Use the number box for precision or the slider for fast scenario testing.
Scenario results
Combined duration
4 h 20 min
Normalized hours and minutes.
Decimal hours
4.3333
Useful for timesheets.
Rounded billable time
4.5 hours
Rounded up to 15-minute increments.
How the calculation works
Use consistent units and retain full precision until the final display step.
Worked example
Reproduce the displayed scenario, then change one assumption at a time.
Assumptions behind the result
- • Inputs use the units shown beside each control.
- • The displayed formula is applied without hidden market or demographic data.
- • Rounding occurs only for display; calculations keep full numeric precision.
- • Sixty minutes make one hour; decimal 1.50 hours means 1 hour 30 minutes, not 1 hour 50 minutes.
- • This tool adds durations and does not handle calendar dates, daylight-saving changes, or time zones.
Mistakes that change the answer
- • Mixing percentages with decimals or mixing incompatible units.
- • Relying on a rounded intermediate value instead of the full result.
- • Changing several assumptions at once instead of testing first duration hours separately.