How to use the time duration calculator
Enter start and end clock times. Select next day for an overnight interval such as 10:00 PM to 6:00 AM.
Time-duration method
Decimal hours divide total minutes by 60. For example, 7 hours 30 minutes equals 7.5 decimal hours.
Example: Lucas measures an overnight interval
Lucas starts at 10:00 PM and finishes at 6:00 AM the next day. Selecting Next day produces 8 hours, equivalent to 480 minutes.
The same clock times on the same day would put the end before the start. This tool compares clock readings and does not adjust for time zones or daylight-saving changes.
Same-day and overnight time differences
For a same-day interval, the end time follows the start time on the same calendar date. For an overnight interval, the end time is treated as occurring on the following day.
That distinction matters for shifts such as 10:00 PM to 6:00 AM. Without the overnight setting, the raw clock difference would appear negative or ambiguous.
Decimal hours are useful for payroll and billing
Minutes can be converted to a fraction of an hour by dividing by 60. For example, 7 hours 30 minutes equals 7.5 decimal hours, while 7 hours 15 minutes equals 7.25 hours.
Decimal hours are not the same as hours-and-minutes notation, so 7.30 hours means 7 hours 18 minutes rather than 7 hours 30 minutes.
Assumptions and limitations
What the estimate assumes
Does not apply time zones, daylight-saving transitions, or dates.
Time Duration Calculator FAQs
How do I calculate an overnight time span?
Select that the end time occurs on the next day.
What are decimal hours?
Total minutes divided by 60. Thirty minutes equals 0.5 hour.
Does this subtract breaks?
Use the Hours Worked Calculator when you want to subtract an unpaid break.
Does daylight saving time affect this?
This is a clock-time calculation without dates or time zones, so DST is not modeled.
How do I calculate an overnight time difference?
Treat the end time as occurring on the next day. The calculator's overnight option adds the date rollover before calculating elapsed time.
How do I convert minutes to decimal hours?
Divide the minutes by 60 and add that fraction to the whole hours. Thirty minutes is 0.5 hour; 15 minutes is 0.25 hour.
Clock-time calculation only. Dates, time zones, and daylight-saving transitions are not included.