Duration Calculator (Time Addition)
NewAdd or subtract a list of HH:MM:SS time durations — like video clip lengths or work time logs — and get the running total in HH:MM:SS, total seconds, and decimal hours.
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Total (HH:MM:SS)
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Total seconds
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Decimal hours
Parsed entries
Frequently Asked Questions
How is this different from the Date Difference Calculator?
The Date Difference Calculator finds the gap between two specific calendar dates; this tool instead sums (or subtracts) a list of standalone durations like "1:24:10" or "45:30" — useful for totaling video clip lengths, billable work hours, or workout segment times, none of which are tied to specific dates.
What formats can I enter each duration in?
HH:MM:SS (e.g. "1:24:10"), MM:SS (e.g. "45:30"), or a bare number of seconds — prefix any line with a minus sign to subtract that duration from the running total instead of adding it.
Why does the tool show both HH:MM:SS and decimal hours?
HH:MM:SS is the natural format for reading a total duration, while decimal hours (e.g. 2.25 instead of 2:15:00) is what most timesheet, invoicing, and payroll systems expect when you need to multiply by an hourly rate.
What happens if I enter an invalid line?
It's skipped and flagged in red in the per-line breakdown with a clear warning message, while every other valid line still contributes correctly to the total — so one typo doesn't silently corrupt your whole sum.
Can the total go negative?
Yes — if your subtracted durations (lines starting with "-") outweigh your added ones, the total and its HH:MM:SS representation are both shown with a leading minus sign.