Time Calculator
Add or subtract two time values in hours, minutes, and seconds.
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How to use this calculator
- 1
Enter the first time value in hours, minutes, and seconds.
- 2
Select whether to add or subtract.
- 3
Enter the second time value.
- 4
The result appears in H:MM:SS format along with total hours, minutes, and seconds.
Frequently asked questions
Can the result be longer than 24 hours?
Yes. There is no clock wrap-around, so 30 hours stays 30 hours. This is what you want for weekly timesheets and long travel legs, and it is also why the tool cannot tell you “next day, 6:00 AM”.
What if I enter more than 59 minutes or seconds?
Everything is converted to seconds first, so 0 h 90 min 75 s is read as 5,475 seconds and displayed as 1:31:15. You do not have to normalise the fields yourself.
How do I find the time between two clock times?
Enter the later time as A, the earlier time as B and choose Subtract: 17:30 minus 9:15 is 8:15:00. If the span crosses midnight, add 24 to the later time first. For 22:00 to 06:00, enter 30 hours as A and 22 as B to get 8:00:00.
How are negative results shown?
A minus sign is placed in front of the H:MM:SS value and each total. 1:20:00 minus 2:05:15 displays −0:45:15, which is −0.75 hours and −2,715 seconds.
Why do the totals not always match the H:MM:SS value exactly?
Total hours is rounded to two decimals (8 h 20 min shows 8.33 h) and total minutes drops the leftover seconds rather than rounding, so 1:31:15 shows 91 min. Total seconds is exact.
Can I enter fractions such as 1.5 hours or 30.5 seconds?
Decimal hours work: 1.5 in the hours field is read as 1:30:00. A fractional seconds value is kept, so 30.5 seconds displays as 0:00:30.5, and the sum is rounded to the nearest thousandth of a second so that 1.1 hours plus 2.2 hours reads 3:18:00 rather than a long decimal tail. Stick to whole seconds for a clean H:MM:SS result.
Does it handle AM/PM, time zones or daylight saving?
No. It adds and subtracts durations only. Convert 12-hour times to 24-hour form yourself, and note that a clock change during your interval is not accounted for. Only two values go in per calculation, so chain results for longer lists.
Time calculator — adding and subtracting hours, minutes and seconds
Base 60 is the whole problem
Hours, minutes and seconds carry at 60, not 10, so ordinary column addition gives wrong answers: 45 minutes plus 50 minutes is not 95 minutes of anything useful. The calculator turns both values into seconds, adds or subtracts, and converts back. That is why oversized fields are fine and why the result is always a clean H:MM:SS value. Hours are never capped, so a total of 40 hours appears as 40:00:00 rather than wrapping to a clock face, which is what you want for workweeks, flight legs and audio or video running times.
Worked examples
Each row was produced by running the calculator with the fields shown. The 0:90:75 row types 90 into the minutes box and 75 into the seconds box, and the last row types decimal hours. The 40-hour row shows a long running total losing leftover seconds in the total-minutes figure: 99,570 seconds is 1,659 whole minutes plus 30 seconds.
| Calculation | Result | Total hours | Total seconds |
|---|---|---|---|
| 2:45:30 + 3:50:45 | 6:36:15 | 6.60 h | 23,775 |
| 1:30:00 + 1:30:00 | 3:00:00 | 3.00 h | 10,800 |
| 17:30:00 − 9:15:00 | 8:15:00 | 8.25 h | 29,700 |
| 1:20:00 − 2:05:15 | −0:45:15 | −0.75 h | −2,715 |
| 0:90:75 + 0 | 1:31:15 | 1.52 h | 5,475 |
| 7:45:00 + 8:30:00 | 16:15:00 | 16.25 h | 58,500 |
| 40:00:00 − 12:20:30 | 27:39:30 | 27.66 h | 99,570 |
| 1.1 h + 2.2 h | 3:18:00 | 3.30 h | 11,880 |
Timesheets and decimal hours
Payroll systems often want decimal hours, not H:MM. A shift of 8 hours 15 minutes is 8.25 hours, but 8 hours 20 minutes is 8.33, a repeating fraction, so the two-decimal figure is rounded. Add the shifts as durations first and convert once at the end; rounding each day separately can leave the weekly total a few hundredths off. Two shifts of 7:45 and 8:30 total 16:15:00, which is 16.25 hours and exactly representable, whereas 8:20 is not.
Elapsed time across midnight
Subtracting a clock time from an earlier one gives a negative number, which is the signal that the interval crossed midnight. Add 24 hours to the end time and subtract again: 30:00 minus 22:00 is 8:00:00, the length of a night shift running 10 PM to 6 AM. For spans longer than a day, use the date difference calculator with real dates instead.
Limits worth knowing
The inputs are durations, not times of day, so AM and PM, time zones and daylight saving changes are outside its scope. Fractional seconds are passed through as typed, and only two values can be combined per calculation. To total a list of laps or shifts, add the first two, copy the result into A, and carry on with the next one. An emptied box counts as zero, so leaving every field blank returns 0:00:00 and subtracting a value from itself does too, with no minus sign on a zero result.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →