1
Both inputs become seconds first
Hours are multiplied by 3,600 and minutes by 60. Integer seconds are then added or subtracted before the result is decomposed into normalized units.
Time Duration Calculator
Add and subtract hours, minutes, and seconds to calculate total durations and elapsed time.
Tested tool guide
Math and conversion tools
Checked July 30, 2026
What Time Duration Calculator does, with a checked example
The duration calculator combines two nonnegative hour, minute, and second inputs. Addition joins the elapsed amounts; subtraction removes Duration B from Duration A and can return a negative result. The output normalizes overflow into days, hours, minutes, and seconds and also reports total seconds and decimal hours.
Worked example
A concrete input and expected output from the current implementation.
Input
Duration A 1h 45m 0s; add Duration B 2h 30m 0s
Expected output
04:15:00; 15,300 total seconds; 4.25 decimal hours
Seventy-five combined minutes normalize to one hour and fifteen minutes, so the total becomes four hours and fifteen minutes.
How the result is produced
2
Clock form can exceed 24 hours
The HH:MM:SS display uses total hours, so a two-day result begins with 48 rather than wrapping to 00. Separate day and hour cards provide the decomposed view.
Good uses
- Total two work, media, or exercise intervals.
- Subtract a break from an elapsed duration.
- Convert a compound duration to decimal hours.
Limits and checks
- A duration is not a wall-clock time or timezone-aware date.
- Inputs are treated as elapsed units even when minutes exceed 59.
- Negative output means the subtracted duration was larger.
Common questions
Can minutes be greater than 59?
Yes. The input is converted to seconds and normalized, so 90 minutes becomes one hour and thirty minutes in the result.
Does the calculator handle daylight-saving changes?
No. It works with elapsed durations. Use a date-time tool with timezone rules when comparing actual clock timestamps.
References and verification
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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