Speed Converter

Convert between kilometres per hour, miles per hour, metres per second, knots, and other speed units. Knots measure nautical miles per hour and are used in aviation and at sea. One knot equals exactly 1.852 km/h. Select your units and enter a speed, or open a conversion page to see its factor and examples.

Speed Conversion Guide

Understanding Speed Measurements

Speed is distance per unit time, a derived SI quantity measured in metres per second (m/s). The kilometre per hour (km/h) is derived from SI but is not itself an SI unit; it is used in most of the world for road speeds. The knot (1 nautical mile per hour = 1.852 km/h exactly) is the unit of speed in aviation and maritime navigation worldwide. Miles per hour (mph) is used in the US and UK. Mach 1 is approximately 340 m/s at sea level and 15 °C, varying with air density and temperature.

All conversions in this category are computed relative to a single base unit (Meters per Second) using factors sourced from NIST Special Publication 811 and the BIPM SI Brochure. A shared reference unit keeps the conversion relationships consistent. Converting directly from the original measurement avoids the rounding differences that can accumulate when displayed intermediate results are entered again.

Common Speed Units

This calculator supports 7 units, including Meters per Second, Kilometers per Hour, Miles per Hour, Feet per Second, Knot. Choose the unit shown in your source measurement, then the unit needed for your result.

Units may have alternate spellings or abbreviations. You can search using these names too. Examples include Meters per Second (mps, also written as m/s or meters/second), or Kilometers per Hour (kph, also written as km/h or kmh), or Miles per Hour (mph, also written as mi/h or miles/hour).

How to Convert Speed Accurately

All speed conversions within the SI family are purely multiplicative: you multiply the source value by a fixed conversion factor derived from the ratio of the two unit definitions. Imperial-to-metric conversions use the exact defined equivalences (e.g., 1 inch = 25.4 mm exactly) rather than approximations.

When precision matters, avoid rounding intermediate calculations. The displayed factors and results are rounded for readability, usually to ten significant digits; very large or small values use scientific notation. Use the original measurement for each conversion and round the final answer to match the accuracy of that measurement.

Checking Your Speed Conversion

Keep the unit alongside each speed value when you copy or share it. Check that the source and target units match your task. If two units have similar names, read their definitions before selecting one.

For a second check, use the worked example and formula on the conversion page. Start from your original value rather than a rounded result from another calculator. If you need to report a specific number of decimal places, round once at the end.

Available Speed Units

See full definitions in the unit glossary →

Meters per Second(mps)

Also: m/s, meters/second

Kilometers per Hour(kph)

Also: km/h, kmh

Miles per Hour(mph)

Also: mi/h, miles/hour

Feet per Second(fps)

Also: ft/s, feet/second

Knot(knot)

Also: knots, kn

Mach(mach)

Also: mach number

Speed of Light(c)

Also: light speed

Popular Speed Converters

Choose a pair below, or browse the full list for other units.

Meters per Second to Kilometers per Hourmps to kph Meters per Second to Miles per Hourmps to mph Meters per Second to Feet per Secondmps to fps Meters per Second to Knotmps to knot Meters per Second to Machmps to mach Kilometers per Hour to Meters per Secondkph to mps Kilometers per Hour to Miles per Hourkph to mph Kilometers per Hour to Feet per Secondkph to fps Kilometers per Hour to Knotkph to knot Miles per Hour to Meters per Secondmph to mps

All Speed Converters

Each page has a calculator, a formula, and examples you can check by hand.

Meters per Second to Kilometers per Hourmps ⇄ kph Meters per Second to Miles per Hourmps ⇄ mph Meters per Second to Feet per Secondmps ⇄ fps Meters per Second to Knotmps ⇄ knot Meters per Second to Machmps ⇄ mach Kilometers per Hour to Meters per Secondkph ⇄ mps Kilometers per Hour to Miles per Hourkph ⇄ mph Kilometers per Hour to Feet per Secondkph ⇄ fps Kilometers per Hour to Knotkph ⇄ knot Miles per Hour to Meters per Secondmph ⇄ mps Miles per Hour to Kilometers per Hourmph ⇄ kph Miles per Hour to Feet per Secondmph ⇄ fps Miles per Hour to Knotmph ⇄ knot Feet per Second to Meters per Secondfps ⇄ mps Feet per Second to Kilometers per Hourfps ⇄ kph Feet per Second to Miles per Hourfps ⇄ mph Knot to Meters per Secondknot ⇄ mps Knot to Kilometers per Hourknot ⇄ kph Knot to Miles per Hourknot ⇄ mph Mach to Meters per Secondmach ⇄ mps

Speed Converter FAQ

How many speed units are supported?

This category supports 7 units: Meters per Second, Kilometers per Hour, Miles per Hour, Feet per Second, Knot, Mach, Speed of Light.

How do I convert speed units?

Choose a source and target unit, enter a value, and multiply through the mps base-unit factors shown on the dedicated converter page.

Which speed conversion should I start with?

Choose the pair that matches your measurement. For example, the Meters per Second to Kilometers per Hour page shows its formula and worked examples. Related links let you reverse the conversion or choose another unit.

Can I look up speed values in a reference table?

Yes. Open a conversion pair to see worked examples and a table of common input values. These reference values remain readable without running the interactive calculator. For an input not listed, use the displayed formula or enter it in the calculator.

How should I round a speed conversion?

Match the precision of your original measurement. Keep extra digits during the calculation, then round the final answer to the required decimal places or significant figures. Displaying more digits does not make the original measurement more accurate.