How to Convert Speed
Enter the speed value in the Value field.
Select the unit you are converting from in the From list.
Select the unit you want to convert to in the To list.
The result appears instantly below the unit selectors.
Key Features
31 Speed Units
Covers everyday units (km/h, mph, m/s), maritime and aviation units (knots, Mach), metric subdivisions (cm/s, mm/min), and extreme units (speed of light, cosmic velocities).
High Precision
Conversions use precise multipliers with up to 10 significant figures. Scientific notation is applied automatically for very large or very small values.
Works Offline
All conversions run entirely in your browser using JavaScript. No internet connection is needed after the page loads.
Privacy-First
No data is ever sent to a server. Your values stay on your device.
Privacy & Security
This tool runs entirely in your browser. No values are transmitted to any server, stored, or logged. It is safe to use in offline environments.
Frequently Asked Questions
What is the base unit used for conversions?
All conversions use meter/second (m/s) as the base unit. Each unit has a known multiplier to convert to m/s, so any unit pair can be converted via: result = value × fromMultiplier ÷ toMultiplier.
What does Mach 1 equal in km/h?
Mach 1 (at 20°C, 1 atm) equals approximately 1236.96 km/h or 768.1 mph. The speed of sound varies with temperature and medium.
What is a knot?
A knot is a unit of speed equal to one nautical mile per hour, approximately 1.852 km/h or 1.151 mph. It is used in maritime and aviation navigation.
How fast is the speed of light in km/h?
The speed of light in a vacuum is exactly 299,792,458 m/s, which equals approximately 1,079,252,849 km/h.
What is the difference between knot and knot (UK)?
The international knot (1.852 km/h) is the modern standard. The UK admiralty knot (1.85318 km/h) was an older definition based on the UK nautical mile and is now obsolete.