Time Calculator
Add or subtract hours, minutes, seconds. Time differences.
Result
4:15:15
A time calculator adds and subtracts durations in hours, minutes, and seconds, and finds the difference between two times, without the arithmetic headaches of base-60.
Enter your times or durations and choose to add, subtract, or find the difference. The tool carries and borrows across the 60-minute and 60-second boundaries and returns a clean result.
Time math is error-prone by hand because minutes and seconds roll over at 60, not 100. Letting the calculator handle the carrying avoids the usual mistakes.
How this calculator works
The calculator converts each time or duration into a single unit, typically total seconds, performs the addition or subtraction, then converts the result back into hours, minutes, and seconds. Working in one unit is what makes the carrying automatic: 90 seconds becomes 1 minute 30 seconds, and 75 minutes becomes 1 hour 15 minutes. For the difference between two clock times, it accounts for spans that cross midnight by adding a full day (86,400 seconds) when the end time is earlier than the start time.
What affects the number
- Minutes and seconds roll over at 60, so carrying and borrowing differ from ordinary decimal math.
- Spans that cross midnight need a day added, or the difference comes out negative.
- Mixing 12-hour and 24-hour formats is a common source of error; pick one consistently.
- Whether you include or exclude seconds affects precision for short durations.
- Adding many durations accumulates carries, which the single-unit method handles cleanly.
- Time zones are separate from duration math and should be handled before subtracting clock times.
Frequently asked questions
How do I add hours and minutes?
Add the seconds, then the minutes, then the hours, carrying any total of 60 or more up to the next unit. For example, 1:45 plus 0:30 is 2:15. The calculator does the carrying automatically so you avoid base-60 mistakes.
How do I calculate time between two times?
Subtract the start from the end. If the end is earlier, as with an overnight span, add 24 hours first. From 10:30 PM to 6:15 AM is 7 hours 45 minutes once the day boundary is accounted for.
Can it handle times that cross midnight?
Yes. When the end time is earlier than the start time, the calculator adds a full day so the difference reflects an overnight span correctly, rather than returning a negative duration.
What is the difference between a time and a duration?
A time is a point on the clock, like 3:00 PM. A duration is a length, like 2 hours 30 minutes. The calculator can add a duration to a time, or subtract two times to produce a duration.
This calculator provides general estimates for educational purposes only and is not financial, medical, legal, or tax advice. Your actual results depend on your specific situation and current rates.