Time Calculator

Convert both durations to a single unit, usually seconds, then add or subtract, then convert the result back to hours, minutes, and seconds. For example, adding 2 hours 45 minutes to 1 hour 30 minutes: 2h45m is 9,900 seconds, 1h30m is 5,400 seconds, and 9,900 plus 5,400 is 15,300 seconds, which converts back to 4 hours 15 minutes.

If you only ever need to add durations together, or only ever need to subtract one from another, the dedicated Add Time Calculator and Subtract Time Calculator offer the same math in a simpler, single-purpose form.

Convert the duration to seconds, multiply or divide by your factor, then convert back. For example, multiplying 2 hours 30 minutes by 3: 2h30m is 9,000 seconds, and 9,000 times 3 is 27,000 seconds, which converts back to 7 hours 30 minutes. Dividing the same duration by 3 instead gives 3,000 seconds, or 50 minutes.

This is useful for scaling a single task's time up or down, such as estimating how long 5 repetitions of a 12-minute job will take, or splitting one long duration into several equal parts.

On Subtract, the result can go negative if Duration 2 is longer than Duration 1, for example subtracting 2 hours from 1 hour. The calculator shows this as a minus sign in front of the result, such as -1h 0m 0s, rather than an error, so you can see exactly how far past zero the difference goes.

Payroll and timesheet software usually wants a duration expressed as a single decimal number of hours rather than hours and minutes separately, for example 7.5 hours instead of 7 hours 30 minutes. Take the result from this calculator and run it through the Hours to Decimal Calculator to get that decimal figure directly.

This calculator works with durations you already know, such as 2 hours 30 minutes. If instead you have two clock times, like 9:00 AM and 5:30 PM, and want to know the elapsed time between them, use the Time Difference Calculator instead, it handles that clock-to-clock math directly, including spans that cross midnight.