Time Calculator
Add or subtract two time values with hours, minutes, and seconds.
Time arithmetic
Result:
How time arithmetic works
Since time doesn't use base-10 like ordinary numbers (60 seconds per minute, 60 minutes per hour), the calculator first converts both time values entirely into seconds, performs simple addition or subtraction on those totals, then converts the result back into hours, minutes, and seconds — this avoids the manual "borrowing" and "carrying" needed when adding or subtracting time values directly in HH:MM:SS form.
Frequently asked questions
Why does subtraction show 00:00:00 instead of a negative result? This calculator floors negative results at zero, since a negative duration isn't a meaningful real-world time span — if you need a signed difference, swap the order of the two times so the larger one is entered first.
Can I use this to add up multiple time entries? For more than two entries, add them two at a time (or track a running total offline) — this tool is built around a single add/subtract operation between two time values.
Is this the same as calculating elapsed time between two clock times? Not quite — this adds or subtracts two durations (like "1h 30m" and "45m"), while elapsed time between clock times (like 9:00 AM to 5:00 PM) is a related but different calculation, covered by the Hours Calculator.