Time Calculator
Add, subtract, multiply or divide durations in hours, minutes and seconds, or move a clock time forward or back across midnight.
Result
Result: 4:16:15
Minutes and seconds past 59 are carried. A clock result is a time of day with no date; the day count says how many midnights it crossed.
- Total seconds
- 15,375
- Decimal hours
- 4.2708
https://calcgallery.com/date-time/time-calculator/
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How to use the Time Calculator
- Choose what to do. Two durations can be added or subtracted, one duration can be multiplied or divided by a number, or a clock time can be moved forward or back.
- Enter hours, minutes and seconds in separate boxes. Minutes and seconds may go past 59; 90 minutes is carried as an hour and a half.
- Read the result as hours, minutes and seconds, with the total in seconds and in decimal hours. For a clock time, read the new time and how many days away it lands.
Everything becomes seconds first
Hours, minutes and seconds are a base-60 system, so adding them like ordinary decimals goes wrong. 1:30 plus 1:45 is 2 hours 75 minutes, which is 3:15 once the extra hour is carried. Typed as the decimals 1.30 and 1.45 instead, the sum is 2.75, and reading 2.75 as 2:45 is half an hour short. The page converts each duration to seconds, does the arithmetic once, and only then writes the answer back out.
seconds = hours × 3600 + minutes × 60 + secondsresult = a + b, a − b, a × n or a ÷ nclock = (start + duration) wrapped into 0 to 24 hoursBecause the entries are only added up, a minute value of 90 or a second value of 150 is not an error. It is carried into the next unit exactly as it would be on paper.
Durations and times of day are different things
A duration is an amount of time: 26 hours is a perfectly good duration. A time of day is a reading on a clock, which starts again at midnight. When you add a duration to a clock time, the page wraps the result into a single day and reports the number of midnights crossed separately. It works with the clock as written and knows nothing about time zones or a daylight saving change, which can make a real day 23 or 25 hours long.
Rounding
The arithmetic is not rounded; only the display is. The total in seconds is shown to three decimal places and the decimal hours to four, and the hours-minutes-seconds text is rounded to the nearest thousandth of a second. The seconds only lose anything after a division or a fractional multiplier, but the decimal hours are often rounded, since a single minute is 0.016666… of an hour and shows as 0.0167. If you need the answer as decimal hours for a timesheet, the time to decimal calculator converts either way.
With your numbers
- First duration = 9,930 s
- 9,930 s + 5,445 s = 15,375 s
- Result = 4:16:15
Quick reference
Minutes and seconds past 59 are carried. A clock result is a time of day with no date; the day count says how many midnights it crossed.
| Example | Result |
|---|---|
| 2:45:30 plus 1:30:45 | Result: 4:16:15 |
| 2:45:30 minus 1:30:45 | Result: 1:14:45 |
| 1:30:45 minus 2:45:30 | Result: −1:14:45 |
| 2:45:30 times 3 | Result: 8:16:30 |
| An hour divided by 7 | Result: 0:08:34.286 |
| 90 minutes and 90 seconds, normalised | Result: 1:31:30 |
| 22:30 plus 3 hours 45 minutes | Clock time: 2:15 AM |
| 01:00 minus 2 hours | Clock time: 11:00 PM |
| 09:00 plus 50 hours | Clock time: 11:00 AM |
Common questions about the Time Calculator
- How do I add times together?
- Turn each into seconds, add the seconds, then split the total back into hours, minutes and seconds. 2 hours 45 minutes 30 seconds is 9,930 seconds; 1 hour 30 minutes 45 seconds is 5,445; together 15,375 seconds, which is 4 hours 16 minutes 15 seconds. Adding the columns directly works too, as long as every 60 seconds is carried into a minute and every 60 minutes into an hour.
- Can the answer be negative?
- Yes. Taking a longer duration from a shorter one leaves a negative result, shown with a minus sign, rather than silently swapping the two. That is what you want when working out how far behind a schedule you are.
- How do I split a time into equal parts?
- Choose divide and enter the number of parts. An hour shared seven ways is not a whole number of seconds, so the result shows the fraction of a second to three places. The page divides the full value and rounds only what it displays.
- What happens when a clock time passes midnight?
- The clock wraps round to 00:00 and the day count goes up by one. Adding 3 hours 45 minutes to 22:30 gives 02:15 on the next day, shown as a day count of 1. Going back past midnight gives a negative count. The page has no calendar, so it cannot say which date that is; the date add and subtract calculator can.
- How is this different from the hours and minutes calculator?
- The hours and minutes calculator adds or subtracts two durations in whole minutes. This page also handles seconds, multiplication and division, and moving a time of day. For the time between two clock readings, such as a shift, use the time duration calculator.