Everyday
Time Duration Calculator
Calculate the elapsed duration between two clock times, including an overnight interval when the end time is earlier than the start time.
- Free to use
- Runs in your browser
- Level A · Standard formula
- Last reviewed 2026-08-16
Calculator guide
How to use the Time Duration Calculator
Calculate the elapsed duration between two clock times, including an overnight interval when the end time is earlier than the start time. Enter the requested values and select Calculate. The result and supporting values are produced locally in your browser.
Formula
Worked example
From 9:15 AM to 5:45 PM is 8 hr 30 min, or 510 minutes.
What to keep in mind
- If the end time is earlier than the start time, the calculator assumes the interval crosses midnight.
- This calculator measures clock time only; it does not account for time-zone or daylight-saving transitions.
Methodology
This calculator uses deterministic arithmetic and performs the calculation locally in your browser. Verify assumptions, units, and source values for your specific use case.
Review standard: Level A · Standard formula. How calculator reviews work.
Frequently asked questions
What does this calculator calculate?
Calculate the elapsed duration between two clock times, including an overnight interval when the end time is earlier than the start time.
How is the result calculated?
Duration = End Time − Start Time; if End < Start, add 24 hours.
Can I use the result for an important decision?
Use the result as a calculation aid and verify the inputs, assumptions, and applicable professional or regulatory requirements before relying on it for an important decision.
Does CalculateMeasure store the values I enter?
The calculator performs its arithmetic in your browser. The calculator itself does not need to send your entered values to a server to produce the result.