Speed Converter

Free speed converter: convert between miles per hour, kilometers per hour, meters per second, knots, feet per second, and Mach speed instantly.

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This tool has a free JSON API. Copy a prompt or skill below to use it with ChatGPT, Claude, or any AI agent — no API key needed.

API docs
Enter a value to convert.

How speed converter works

This converter handles common speed units used in everyday life, aviation, and physics. It works by first converting the input to meters per second (the base unit), then dividing by the target unit factor. For example, 1 mph equals 0.44704 m/s, and 1 km/h equals 0.277778 m/s.

The supported units are meters per second (m/s), kilometers per hour (km/h), miles per hour (mph), knots (nautical miles per hour), feet per second (ft/s), and Mach (the speed of sound, approximately 343 m/s at sea level).

This is useful for driving, aviation, sailing, cycling, and physics. The most common conversion is mph to km/h for international travel. Results are rounded to six decimal places.

Frequently asked questions

How do I convert mph to km/h?
Multiply the mph value by 1.60934. For example, 60 mph times 1.60934 = 96.56 km/h. The converter does this automatically.
How do I convert km/h to mph?
Divide the km/h value by 1.60934 (or multiply by 0.621371). For example, 100 km/h / 1.60934 = 62.14 mph.
What is a knot?
A knot is one nautical mile per hour, equal to 1.852 km/h or 1.15078 mph. Knots are used in aviation and maritime navigation.
What is Mach speed?
Mach is the speed of sound, approximately 343 meters per second at sea level at 20 degrees Celsius. Mach 1 equals the speed of sound; Mach 2 is twice the speed of sound.