How to Use the Time Duration Calculator
- Choose Time only for two clock times, or Date & time when the interval includes calendar dates.
- Enter the starting value and ending value. Use the next-day checkbox for a time-only interval that crosses midnight.
- Choose whether seconds should be included, then select Calculate Duration.
- Read the duration breakdown and total hours, minutes, seconds, and decimal equivalents. Use Copy Results to copy a text summary.
Time Duration Calculation Formula
For two complete date-time values, the basic formula is elapsed duration = end date-time − start date-time. The calculator determines the difference in seconds and then converts that duration into days, hours, minutes, and seconds.
In Time only mode, clock times are measured from midnight. When the next-day option is enabled and the end time is earlier than or equal to the start time, one 24-hour day is added to the end time before subtraction. This makes equal times represent 24 hours when the next-day option is selected.
Examples of Time Duration Calculations
Same-day duration
From 09:15 to 17:45 on the same day is 8 hours and 30 minutes. That equals 8.50 decimal hours, 510 minutes, or 30,600 seconds.
Overnight duration
From 22:30 to 06:15 the next day is 7 hours and 45 minutes. Enable the next-day option in Time only mode to calculate this interval.
Multi-day duration
From 2026-10-20 at 09:00 to 2026-10-22 at 14:30 is 2 days, 5 hours, and 30 minutes in a time zone without a clock change during that interval. The elapsed total is 53.5 hours, 3,210 minutes, or 192,600 seconds.
Decimal hours
To convert minutes to decimal hours, divide the total minutes by 60. For example, 90 minutes ÷ 60 = 1.50 hours. Use the decimal result when a spreadsheet or time-tracking form requests hours as a decimal number.
Common Uses of a Time Duration Calculator
Use the calculator to check meeting lengths, study sessions, event durations, travel segments, project timelines, elapsed time between milestones, and work-shift intervals. It measures elapsed clock time only. If you need paid work hours, subtract breaks separately and follow the relevant workplace rules.
Frequently Asked Questions
1. How do I calculate the duration between two times?
Choose Time only, enter the start and end clock times, and select Calculate Duration. If the end occurs on the next day, enable the next-day option.
2. How do I calculate hours between AM and PM?
Enter each value using the browser's time picker. The underlying calculation uses a 24-hour clock representation, so AM/PM is handled by the time input instead of manual conversion.
3. How do I calculate an overnight time duration?
Enter the start and end times and enable the option that treats an earlier or equal end time as occurring the next day. For example, 22:30 to 06:15 is 7 hours and 45 minutes.
4. How do I calculate the difference between two dates and times?
Select Date & time, enter both dates and clock times, then calculate. The ending date-time must be the same as or later than the starting date-time.
5. How do I convert a duration into decimal hours?
Divide the total elapsed minutes by 60, or divide the total elapsed seconds by 3,600. For example, 90 minutes is 1.50 decimal hours.
6. How do I calculate total minutes or seconds?
The results show total minutes and total seconds for the full interval, not just the leftover minutes or seconds after whole hours are counted.
7. Can I calculate durations spanning multiple days?
Yes. Select Date & time and enter the complete starting and ending dates and times. The result includes the total duration even when it exceeds 24 hours.
8. Does this calculator account for daylight-saving time?
Date & time mode uses the local time-zone rules applied by your browser. A daylight-saving transition can change elapsed time compared with simply subtracting wall-clock labels. Some repeated local times are ambiguous and cannot be selected precisely with a basic local date-and-time input. This calculator does not convert between named time zones.
9. Is this calculator free to use?
Yes. The calculator can be used without an account or payment.
10. Does the calculator store my entered times?
This widget does not intentionally save your inputs or results to a server or browser storage. It calculates within the page. Your website, browser, hosting, caching, analytics, or other installed services may have their own data practices, so consult the website's privacy policy for those details.
This calculator measures elapsed duration between entered values. It is not a time-zone converter, work-hours/payroll calculator, or business-hours calculator.