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Accurately convert between speed units like mph, km/h, m/s, Mach, and the speed of light. Ideal for research, engineering, and daily calculations.
Overview
Understand what the tool solves, how it works, and the boundaries of its data.
Enter a numeric speed, choose its starting unit, and select a destination unit to view the converted value. The available units are meters per second (m/s), kilometers per hour (km/h), miles per hour (mi/h), knots (kn), and feet per second (ft/s). This covers familiar US uses such as mph, along with units used in technical, aviation, and maritime contexts.
A speed conversion changes how the same quantity is expressed. For example, it does not measure a moving object or verify that a speed sensor is calibrated. Display precision controls rounding of the shown result; it does not make the input measurement more accurate.
Guide
Follow the workflow and verify inputs and outputs with practical examples.
Enter the value you want to convert. Use a numeric value in the input field.
Choose the source unit, such as mi/h, and the target unit, such as km/h, from the speed-unit controls.
Set the number of decimal places for the displayed result. Use enough places for your calculation, while keeping the precision of the original measurement in mind.
Read the converted value with its target unit label. Change either unit to compare another representation of the same entered speed.
The underlying relationship is a unit conversion through a common speed basis: multiply the entered value by the source unit’s factor to express it in meters per second, then divide by the target unit’s factor. NIST’s Guide to the SI lists conversion factors for mi/h, km/h, knots, and ft/s relative to m/s.
Use cases
See how the tool fits into real work and everyday tasks.
Convert an mph value to km/h when reading an international specification or preparing a travel note. Keep the original value alongside the conversion if the source matters.
Move between m/s and ft/s or km/h as required by the problem, then retain the units in each step so the final result is easy to interpret.
Q&A
Find concise answers to common questions and confusing cases.
NIST lists 1 mile per hour as 1.609344 kilometers per hour. A displayed result can be rounded to the selected decimal-place setting.
A knot is a nautical mile per hour. NIST lists its conversion to meters per second as 0.5144444…; use the displayed unit and chosen precision when reading a converted value.
No. It changes how many decimal places are displayed, not the accuracy of the measurement you entered. Avoid treating extra digits as evidence of greater measurement certainty.
Notes
Review scope, result limitations, and important precautions before use.
This page converts units for a value you provide; it does not measure speed, validate an instrument, or certify a result for a safety-critical decision. Check the source measurement, required tolerance, and applicable procedure when precision matters. Rounded output should not be reported with greater certainty than the input supports.
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