Time Duration Calculator — Free Online Duration Between Two Times

How to Use the Time Duration Calculator

1. Enter the start time: Fill in the hours (0-23), minutes (0-59), and seconds (0-59) fields under "Start Time." The calculator uses 24-hour format, so 3:30 PM is entered as 15:30:00. The default start time is 09:00:00 (9:00 AM).
2. Enter the end time: Fill in the corresponding fields under "End Time." The default is 17:30:00 (5:30 PM), representing a common workday end time including a half-hour of overtime or a late departure.
3. Review the duration: The results panel immediately displays the calculated duration in a clear H:MM:SS format, along with total minutes, total seconds, decimal hours, and the hours:minutes shorthand. The time range is shown at the bottom for reference.

The calculator updates instantly when any input changes. The seconds field allows for precision timing of athletic events, scientific observations, or video timecodes. For work-hour calculations that do not need seconds, our hours calculator provides a simpler interface.

Duration Calculation Formula

Variables Explained

• H, M, S: Hours, minutes, and seconds components of each time input. Hours range from 0 to 23, minutes and seconds from 0 to 59.
• Total: Each time converted to total seconds from midnight. For 09:15:30, this is (9 x 3,600) + (15 x 60) + 30 = 32,400 + 900 + 30 = 33,330 seconds.
• | | (Absolute value): Ensures the duration is always positive regardless of input order. The difference between 09:00 and 17:00 is the same as between 17:00 and 09:00.
• 3,600: The number of seconds in one hour. Used to convert between total seconds and decimal hours.
• Duration Hours: floor(Total Seconds / 3,600) gives whole hours.
• Duration Minutes: floor((Total Seconds mod 3,600) / 60) gives remaining minutes.
• Duration Seconds: Total Seconds mod 60 gives remaining seconds.

Step-by-Step Example

Calculate duration from 08:15:30 to 14:45:15:

1. Start total: (8 x 3,600) + (15 x 60) + 30 = 28,800 + 900 + 30 = 29,730 seconds
2. End total: (14 x 3,600) + (45 x 60) + 15 = 50,400 + 2,700 + 15 = 53,115 seconds
3. Difference: |53,115 - 29,730| = 23,385 seconds
4. Hours: floor(23,385 / 3,600) = 6 hours (21,600 seconds used)
5. Remaining: 23,385 - 21,600 = 1,785 seconds
6. Minutes: floor(1,785 / 60) = 29 minutes (1,740 seconds used)
7. Seconds: 1,785 - 1,740 = 45 seconds
8. Decimal hours: 23,385 / 3,600 = 6.50 hours
9. Result: 6h 29m 45s (6.50 decimal hours, 23,385 total seconds)

Practical Examples

Example 1: Jake's Marathon Split Analysis

Jake is analyzing his marathon performance. He wants to calculate how long it took him to run from the 20-mile mark to the finish line (26.2 miles). He passed the 20-mile marker at 02:45:12 (elapsed time) and crossed the finish at 03:52:38:

• Start: 02:45:12 (20-mile split)
• End: 03:52:38 (finish time)
• Duration: 1h 07m 26s
• Total seconds: 4,046
• Decimal hours: 1.12

Jake's last 6.2 miles took 1 hour, 7 minutes, and 26 seconds, which gives a pace of approximately 10:50 per mile for the final stretch. This is slower than his earlier pace, indicating he experienced fatigue in the final miles — a common pattern known as "hitting the wall."

Example 2: Dr. Chen's Lab Experiment

Dr. Chen is timing a chemical reaction that starts when a catalyst is added at 10:23:45 and reaches completion (color change) at 10:31:18. She needs the exact reaction time for her research paper:

• Start: 10:23:45 (catalyst added)
• End: 10:31:18 (reaction complete)
• Duration: 0h 07m 33s
• Total seconds: 453
• Total minutes: 7

The reaction took 7 minutes and 33 seconds (453 seconds). Dr. Chen records this as 453 seconds in her lab notebook for consistency with her other measurements. She will compare this to previous trials to determine the average reaction time and standard deviation.

Example 3: Maria's Video Editing Timeline

Maria is editing a documentary and needs to calculate the length of a specific interview segment that starts at the 01:15:42 timecode and ends at 01:28:17:

• Start timecode: 01:15:42
• End timecode: 01:28:17
• Duration: 0h 12m 35s
• Total seconds: 755
• Decimal hours: 0.21

The interview segment is 12 minutes and 35 seconds long. Maria needs to trim it to under 10 minutes for the final cut, so she needs to remove about 2 minutes 35 seconds of content. Knowing the exact duration in seconds helps her plan the edit points precisely in her video editing software. For calculating days between production milestones, our days between dates calculator can help with project scheduling.

Time Unit Conversions Reference Table

Tips and Complete Guide

Choosing the Right Time Calculator

CalculatorGlobe offers several time calculators, each optimized for different use cases. The time duration calculator is best when you need second-level precision and multiple output formats. For simple hour-and-minute calculations (like work shifts), the hours calculator is faster. For adding or subtracting a duration from a base time, the time calculator handles that directly. For comparing two times with directional context, the time difference calculator adds an "earlier/later" indicator. Choose based on whether you need precision (duration calculator), simplicity (hours calculator), arithmetic (time calculator), or comparison (difference calculator).

Time Duration in Sports and Athletics

In athletics, precise time measurement determines winners and records. Olympic sprinting is timed to the thousandth of a second, though this calculator works to whole seconds. Common athletic durations to reference: a world-class 100m sprint is under 10 seconds, a mile run averages 4 minutes for elite runners, a marathon world record is about 2 hours, and an Ironman triathlon takes 8-17 hours for most finishers. Coaches use split times to analyze pacing strategy, and this calculator helps athletes review their segment durations after training sessions.

Using Duration Data for Productivity

Tracking how long tasks actually take (versus how long you estimated) is a powerful productivity technique. Time each task by noting its start and end times, then use this calculator to find the exact duration. Over several weeks, you will develop accurate time estimates for recurring tasks. Research shows that people consistently underestimate task duration by 25-50% (the planning fallacy). Having real duration data helps you create realistic schedules and meet deadlines more reliably.

Common Mistakes to Avoid

• Mixing up AM/PM in 24-hour format: Remember that 3:00 PM is 15:00, not 3:00. Entering 3 instead of 15 creates a 12-hour error in your duration calculation.
• Forgetting seconds when they matter: For casual time tracking, seconds may be negligible. But in sports timing, scientific experiments, or video editing, even a few seconds make a significant difference. Always include seconds in precision-critical calculations.
• Assuming overnight calculations are handled: This calculator computes the absolute difference between two times within a 24-hour period. For overnight durations, use the hours calculator with its Crosses Midnight toggle to get the correct result.
• Converting decimal hours incorrectly: Remember that 0.50 decimal hours is 30 minutes (not 50 minutes). The decimal represents a fraction of 60 minutes, not a percentage out of 100.
• Not using total seconds for calculations: When computing rates or speeds, use total seconds rather than converting back and forth between hours, minutes, and seconds. For example, to find speed: distance / total seconds = units per second.

Frequently Asked Questions