The Time Duration Calculator adds and subtracts lengths of time. Enter durations in days, hours, minutes, and seconds, choose whether each is added or subtracted, and get the total — shown as a readable duration, as HH:MM:SS, and as decimal hours and total minutes/seconds.
It is handy for adding up timesheet entries, working out total run or study time, combining video or task durations, or subtracting a break from a shift. Everything is calculated instantly in your browser.
How to add or subtract time durations
- Enter your first duration in days, hours, minutes, and/or seconds.
- Add more rows and set each to add (+) or subtract (−).
- Read the total as a readable duration, HH:MM:SS, or decimal hours.
- Copy the total with one click.
Adding and subtracting time
Each row is a duration, and you choose whether it is added to or subtracted from the running total. The calculator converts everything to seconds, sums it, and then normalises the result back into days, hours, minutes, and seconds — so 5h 45m plus 2h 30m correctly becomes 8h 15m rather than 7h 75m. If the subtractions outweigh the additions, the total is shown as a negative duration.
Reading the result
The total is shown several ways because different tasks need different formats: a readable duration (like 8h 15m) for quick reading, HH:MM:SS for logs and media, decimal hours (8.25) for billing and payroll, and total minutes or seconds for data entry. Decimal hours are especially useful for timesheets, where 8h 15m is billed as 8.25 hours.
Frequently Asked Questions
How do I add hours and minutes together?
Enter each duration in its own row and keep the operator on +. The tool sums them and normalises the result, so 1h 45m + 30m becomes 2h 15m.
Can I subtract time as well?
Yes. Set a row’s operator to − to subtract that duration. If the result is negative, it is shown as a negative duration.
How do I convert a duration to decimal hours?
The result panel shows decimal hours automatically — for example 8h 15m is 8.25 hours, which is what payroll and billing usually need.
What formats does it show?
A readable duration (8h 15m), HH:MM:SS, decimal hours, total minutes, and total seconds — so you can copy whichever fits.
Is it free and private?
Yes. It is free and runs entirely in your browser, so nothing is uploaded.