Time Calculator
Add or subtract two durations in hours, minutes and seconds, and see the result in each unit — handy for timesheets and splits.
How to use it
- Enter each duration as hours, minutes and seconds.
- Pick add or subtract — negative results are shown with a minus sign.
- The result is also given as a decimal in hours, minutes and seconds.
Examples
| 2:45:30 + 1:20:15 | 4:05:45 |
| 2:45:30 − 1:20:15 | 1:25:15 |
Adding or subtracting clock durations by hand means carrying and borrowing in base 60 rather than base 10 — 45 minutes plus 30 minutes is 75 minutes, which becomes 1 hour 15 minutes, not '75 minutes' left as-is. This tool converts both durations to seconds, does the arithmetic in that flat unit, then converts back, which is exactly the error-prone step people get wrong doing it manually.
Worked example — payroll timesheet
A shift runs 7 hours 40 minutes, with a 35-minute unpaid break to subtract: 7:40:00 − 0:35:00 = 7:05:00 paid time. Converted to decimal for payroll, that's 7 + 5 ÷ 60 = 7.083 hours, not 7.40 hours — a common payroll mistake that comes from reading the minutes digits as a decimal fraction directly.
Clock time vs decimal hours
45 minutes is 0.75 hours, not 0.45 — because a clock runs in 60ths, not 100ths. Payroll and invoicing systems almost always want decimal hours, so converting correctly matters directly for what someone gets paid or billed.
Questions people ask
How do I convert a time to decimal hours for a timesheet?
Divide the minutes by 60 and add them to the hours. 2:45 is 2 + 45 ÷ 60 = 2.75 hours — the 'in hours' tile does it for you.
Is anything sent to a server?
No. Every calculation runs in your browser, so nothing you type is uploaded and the page keeps working offline once it has loaded.
Last updated 17 August 2026