Use this time calculator to find elapsed time between two clock readings or to add and subtract a duration from a . Choose the job first, then enter only the clock readings or duration parts that apply.
How to calculate time between two clock times
Convert the start and end clock readings to the same form, then subtract the start from the end. This calculator converts both readings to first. If the end is earlier on the clock, it adds one before subtracting, so an overnight span stays positive.
Use elapsed for two clock readings, add to find an end time, or subtract to find a start time.
In elapsed mode, an earlier end time is treated as the next .
Enter whole hours and minutes. Open the optional field only when matter.
Add or subtract time from a clock
Add mode counts forward from a known clock reading to find when something ends. Subtract mode counts backward from a known clock reading to find when it started. For example, adding 1 30 to 11:30 PM returns 1:00 AM the next . Subtracting 45 min from 12:15 AM returns 11:30 PM the previous .
Worked example: an overnight shift
Start = 10:30 PM
End = 6:45 AM the next
Elapsed time = End − Start
Elapsed time = 8 15
Decimal hours = 8.25 h
Total minutes = 495 min
Decimal hours and total minutes
Decimal hours express the entire duration as a fraction of an hour. Divide total by 3,600 s/h. An elapsed time of 8 15 is 8.25 h, not 8.15, because 15 min is one quarter of an hour.
Total minutes divide the same duration by 60 s/min. The overnight example is 495 min. These equivalents describe the raw time span; they do not apply workplace break or rounding rules.
Limits of this clock-time calculator
This tool handles clock readings and durations, not calendar dates. It does not model time-zone differences, daylight-saving changes, leap , or spans longer than one overnight rollover in elapsed mode. It also reports a raw clock span without deducting breaks or applying payroll rules. Use a date-duration tool for explicit calendar dates and a work-hours tool when breaks or rounding are part of the question.