Time Calculator
Add or subtract hours, minutes and seconds, or move a clock time forward or back by a duration.
To add two times, add the seconds, minutes and hours separately, then carry every 60 seconds into a minute and every 60 minutes into an hour. 2 hours 45 minutes 30 seconds plus 1 hour 30 minutes 45 seconds is 75 seconds, 75 minutes and 3 hours before carrying, which becomes 4 hours 16 minutes 15 seconds. Subtraction works the same way, borrowing 60 instead of carrying it.
This calculator does plain time arithmetic with 24-hour days. It does not account for time zones, daylight saving changes or leap seconds, and it is not an official payroll record of hours worked.
Result
4h 16m 15s
- Total hours
- 4.2708
- Total minutes
- 256.25
- Total seconds
- 15,375
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About the Time Calculator
Time does not add like ordinary numbers because it counts in sixties. Add 45 minutes to 30 minutes like ordinary numbers and you get 75, a minute count no clock ever shows; the right answer is 1 hour 15 minutes. This calculator does the base-60 bookkeeping for you. The first mode adds or subtracts two durations entered as days, hours, minutes and seconds, then shows the result carried into its proper units along with the same span as total hours, total minutes and total seconds. Total hours is the figure a timesheet or invoice usually wants: 4 hours 16 minutes 15 seconds is 4.2708 hours, or 256.25 minutes. The second mode starts from a time on the clock and moves it forward or back, for questions like when a 9:30 AM start plus 8 hours 45 minutes ends (6:15 PM), or what time it was 3 hours before 1 AM (10 PM the previous day). When the answer crosses midnight the page says how many days it moved. A day here is always 24 hours, so a clock change for daylight saving inside the span is not counted. If you need the hours between two clock times instead, the hours calculator is built for that.
Frequently asked questions
How do I add hours and minutes by hand?+
Add the minutes column and the hours column separately. If the minutes come to 60 or more, take 60 off and add 1 to the hours. 3 hours 50 minutes plus 2 hours 25 minutes is 5 hours 75 minutes, which carries to 6 hours 15 minutes. Seconds carry into minutes the same way.
How do I subtract times when the minutes are smaller?+
Borrow an hour and turn it into 60 minutes. For 5 hours 10 minutes minus 2 hours 40 minutes, 10 minus 40 will not go, so rewrite 5 hours 10 minutes as 4 hours 70 minutes. Then 70 minus 40 is 30 and 4 minus 2 is 2, giving 2 hours 30 minutes.
Why does my regular calculator give the wrong answer for time?+
It works in base 10 and a clock works in base 60. Typing 2 hours 45 minutes as a decimal treats the 45 as hundredths of an hour rather than minutes. Convert minutes to a fraction of an hour first by dividing by 60, or enter hours and minutes in separate boxes as this page does.
What happens when the result goes past midnight?+
In clock mode the new time wraps around the 24-hour face and the page labels it as the next day, the previous day, or a number of days later or earlier. Adding 3 hours to 10 PM gives 1 AM the next day. In duration mode nothing wraps: 30 hours shows as 1 day 6 hours.
Can the result be negative?+
Yes, in duration mode. Subtracting 2 hours 30 minutes from 1 hour leaves minus 1 hour 30 minutes, and the page shows it with a minus sign and a note, rather than quietly swapping the order.
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Free to use on your own site. Paste this snippet where you want the time calculator to appear — it resizes itself automatically.
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