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Time Duration Calculator

Calculate the elapsed time between two times, two dates, or a full date-and-time pair. The Time Duration Calculator shows the result in hours, minutes, and seconds, plus decimal hours, total minutes, and total seconds — and handles overnight spans automatically.

How to Calculate Elapsed Time

Step 1: Convert both the start and end times to 24-hour format. For AM times, keep the hours as-is. For PM times, add 12 to the hour (e.g. 3:30 PM = 15:30).

Step 2: Convert each 24-hour time to a decimal by dividing the minutes by 60 and adding them to the hours (e.g. 15:30 = 15 + 30 ÷ 60 = 15.5).

Step 3: Subtract the start decimal from the end decimal to get the elapsed time in decimal hours.

Step 4: Convert back to HH:MM:SS — multiply the decimal portion by 60 to get minutes, then multiply the remaining decimal by 60 again for seconds.

If the end time is earlier than the start time, the span crosses midnight — add 24 hours to the end before subtracting.

Formula

Duration = End Time − Start Time (in total seconds) Decimal Hours = Duration ÷ 3600

Example:

9:15 AM → 5:45 PM: (17:45 − 09:15) = 8 h 30 m 0 s = 30,600 s = 8.5000 decimal hours

Times Tab — Duration Between Two Times

Enter a start time and an end time to find how many hours, minutes, and seconds separate them within a single day. The calculator shows the result in HH:MM:SS format alongside its decimal hour equivalent, total minutes, and total seconds.

If your end time is earlier than your start time — for example, a night shift from 10:00 PM to 6:00 AM — the calculator treats it as an overnight span and adds a (+1 day) note to the result.

Dates Tab — Duration Between Two Dates

Switch to the Dates tab to find the elapsed time between any two calendar dates. The result is shown as total days, broken down into years, months, and remaining days (approximate), and also expressed as complete weeks plus leftover days.

This is useful when you need a rough sense of how long a period spans in human-readable units — for example, how many months and days are between a project start date and a deadline.

Times & Dates Tab — Exact Duration With Date and Time

The Times & Dates tab combines both inputs: enter a start date with a start time and an end date with an end time. The calculator subtracts the two datetimes and returns the exact duration in days, hours, minutes, and seconds, plus total hours, total minutes, and total seconds.

Use this tab whenever the span crosses one or more full days — for example, from Monday 9:00 AM to Wednesday 2:30 PM — and you need precision down to the second.

Converting Minutes to Decimal Hours

Many payroll systems, billing tools, and spreadsheets expect time in decimal form rather than HH:MM. To convert, divide the minute portion by 60 and add it to the whole hours.

Formula: Decimal Hours = Hours + (Minutes ÷ 60)

• 1 hour 30 minutes = 1 + (30 ÷ 60) = 1.5 hours

• 2 hours 45 minutes = 2 + (45 ÷ 60) = 2.75 hours

• 0 hours 20 minutes = 0 + (20 ÷ 60) ≈ 0.333 hours

The calculator displays the decimal equivalent automatically in every result so you can copy it directly without manual conversion.


See also