How to Use the Time Duration Calculator
Use Time difference for clock times, Date & time for intervals across calendar dates, or Add durations to total several intervals.
Provide the start and end times, or the dates and times required by the selected mode. Check the overnight option if the end time falls on the following day.
Review the elapsed duration, then use decimal hours, total minutes or total seconds when another representation is useful.
Open the calculation steps if you want to see how the hours, minutes and seconds were subtracted or normalized.
How to Calculate Time Between Two Times
The basic time-difference calculation subtracts the starting time from the ending time. Clock time uses 60 minutes per hour and 60 seconds per minute, so the calculation must handle borrowing and normalize the result.
- Start time: 1:30 PM (13:30 in 24-hour notation)
- End time: 3:08 PM (15:08 in 24-hour notation)
- Elapsed time: 1 hour 38 minutes
- Total minutes: 98
- Total seconds: 5,880
- Decimal hours: approximately 1.633333
The result is a duration, not a time of day. An interval that crosses midnight must use an explicit next-day convention rather than treating an earlier end time as automatically valid for every scenario.
Worked Time-Difference Examples
Start: 1:30 PM
End: 3:08 PM
Duration: 1 hour 38 minutes
Total: 98 minutes | 5,880 seconds | 1.6333 decimal hours
Start: 09:30
End: 18:00
Duration: 8 hours 30 minutes
Total: 510 minutes | 30,600 seconds | 8.5 decimal hours
Start: 10:00 PM
End: 2:00 AM (next day)
Duration: 4 hours
Total: 240 minutes | 14,400 seconds | 4.0 decimal hours
Calculate Duration Between Dates
When a duration crosses midnight or spans multiple calendar days, the dates determine how the start and end times relate to each other.
For example, from 10:30 PM on October 12 to 6:15 AM on October 14, the elapsed wall-clock duration is 1 day, 7 hours and 45 minutes, or 31.75 hours (1,905 minutes | 114,300 seconds), under a straightforward calculation without time-zone adjustments.
Calendar dates matter when a calculation crosses the end of a month, a leap day or New Year. Enter valid dates and review the calculator's assumptions before relying on the result.
Convert Time to Decimal Hours, Minutes and Seconds
A duration can be represented as hours, minutes and seconds or as a total number of minutes or seconds. Decimal hours are useful when a duration must be represented numerically, for example in a spreadsheet.
For example, 5 hours, 10 minutes and 30 seconds is:
Do not confuse 5.175 decimal hours with 5 hours and 17.5 minutes, or interpret 5.30 decimal hours as 5 hours 30 minutes. Decimal hours use base 10; clock minutes use base 60.
Add Multiple Time Durations
When several separate durations need to be combined, add their total seconds and convert the sum back into hours, minutes and seconds.
• Segment 1: 1 hour 45 minutes 0 seconds
• Segment 2: 2 hours 30 minutes 0 seconds
• Segment 3: 0 hours 55 minutes 30 seconds
A total duration can exceed 24 hours. It should not wrap to the beginning of a day unless the calculation is explicitly returning a clock time rather than an elapsed duration.
Calculator Assumptions and Limitations
• Input Reference: This calculator finds a duration from the times or date-time values you enter. The same clock time can represent zero elapsed time on the same day or a different duration when the dates differ.
• Overnight Boundary: Overnight calculations require an explicit or documented rule for assigning the end time to the following day. Invalid dates and unsupported input formats must be corrected before a result can be calculated.
• Timezones & Daylight Saving: The date-time mode follows the timezone and daylight-saving assumptions documented in the calculator. Unless explicitly supported, it does not perform a location-based timezone conversion.
• Decimal Output Representation: Decimal-hour output is a numerical representation of the duration; it is not the same as displaying a clock time.
Frequently Asked Questions
How do I calculate the time difference between two times?
Subtract the start time from the end time, accounting for minutes and seconds using base-60 arithmetic. If the interval crosses midnight, use the appropriate next-day rule. The calculator converts the interval into hours, minutes and seconds.
How long is 1:30 PM to 3:08 PM?
The elapsed time is 1 hour and 38 minutes, or 98 minutes in total.
How many hours are there from 09:30 to 18:00?
From 09:30 to 18:00 is 8 hours and 30 minutes, equivalent to 8.5 decimal hours.
How do I calculate time across midnight?
Enter the start and end times and indicate that the end falls on the next day if the calculator requires this option. For example, 10:00 PM to 2:00 AM the next day is 4 hours.
How do I calculate the duration between two dates?
Enter the start date and time and the end date and time in the date-and-time mode. The dates determine whether the interval spans one or more calendar days. Follow the calculator's documented timezone assumptions.
What are decimal hours?
Decimal hours express the duration as a decimal number of hours. For example, 30 minutes equals 0.5 hours, so 5 hours 30 minutes equals 5.5 decimal hours.
How do I add several time durations?
Enter each duration in the multi-segment mode. The calculator sums the intervals and converts the result into hours, minutes, seconds and any other supported units.
Does this calculator deduct unpaid breaks?
Only use the calculator for break deductions if the interface explicitly includes and applies a break-deduction feature. Otherwise, calculate the elapsed time and subtract the relevant break duration separately or use an appropriate time-card calculator.
Related Time Calculators
Use for general time arithmetic and adding or subtracting hours, minutes, and seconds from a clock time.
Use when your main goal is calculating work hours, daily hourly totals, and billable pay rates.
Use if your calculation requires logging multiple employee shifts, in/out punches, and deducting unpaid lunch breaks.
Use when the main task is to add or subtract calendar days, weeks, and months rather than measuring clock time.