Time Duration Calculator

Calculate elapsed time between a start and end time, including overnight periods.

Your duration will appear here.

About the Time Duration Calculator

Clock-time subtraction gets awkward when minutes borrow across an hour or the interval crosses midnight. This calculator finds the elapsed duration cleanly in hours, minutes and seconds.

Clock arithmetic uses 60 minutes per hour and 60 seconds per minute. Treating 8:45 as the decimal number 8.45 gives the wrong result.

How to Use the Time Duration Calculator

  1. Enter the start time and end time using the clock format shown.
  2. Indicate whether the end time occurs on the next day when the interval crosses midnight.
  3. Include seconds only when that level of precision is useful.
  4. Calculate the elapsed duration, then subtract breaks separately if you need net working or billable time.

How the Calculation Works

Each time is converted into a common unit, such as total seconds from midnight. Elapsed time = end total − start total, with a full day added when the supported overnight mode indicates the end is on the following day.

The resulting seconds are converted back into hours, minutes and seconds by dividing by 3,600 for hours and using the remainder for minutes and seconds.

Worked example

Time Duration Calculator Worked Example

9:35 AM to 2:20 PM

From 9:35 to 10:00 is 25 minutes, from 10:00 to 2:00 is 4 hours and from 2:00 to 2:20 is 20 minutes. Total duration = 4 hours 45 minutes.

Result guide

Understanding Your Time Duration Calculator Result

Use elapsed duration for the real interval. If the result is being used for payroll or billing, decide separately whether breaks, rounding rules or overtime thresholds apply.

Before you rely on the answer

Assumptions and Limitations

  • Both times use the same time zone.
  • The overnight setting accurately describes which day the end time falls on.
  • Daylight-saving transitions are not represented unless actual dates and zones are modeled.

Practical tip

Using This Result in Practice

When an interval crosses midnight, write the dates beside the times before calculating. This avoids the common mistake of treating a next-day end time as earlier than the start.

Related calculations

Useful Calculations to Continue With

If you need decimal hours for pay or billing, convert the elapsed duration with the Hours Calculator.

For a compact start-to-end clock calculation, the Hours Between Times Calculator is another direct option.

Common questions

Time Duration Calculator FAQ

How do I calculate a duration that crosses midnight?

Treat the ending time as occurring on the following day. For example, 11:00 PM to 1:30 AM is 2 hours 30 minutes.

Is 2 hours 30 minutes equal to 2.30 hours?

No. Thirty minutes is 0.5 hour, so the decimal equivalent is 2.5 hours.

Should lunch breaks be subtracted?

Only if you want net working or billable time. Calculate the full elapsed interval first, then remove unpaid or excluded breaks.