A speed converter converts a speed value from one unit to another. This converter supports the most common speed units used in road transport (km/h, mph), maritime and aviation navigation (knots), physics (m/s), and aviation (Mach). All conversions use metres per second as the base unit.

1. Enter the speed value.
2. Select the unit you are converting from.
3. Select the unit you are converting to.
4. Click Convert.

100 km/h to mph: 100 × (1/3.6) ÷ 0.44704 = 62.14 mph
20 knots to km/h: 20 × 0.51444 × 3.6 = 37.04 km/h

Knots are used in maritime and aviation contexts. One knot equals one nautical mile per hour. Mach number is the ratio of an object's speed to the speed of sound, which varies with altitude and temperature — this converter uses the sea-level standard value of 340.29 m/s.

• Confusing knots with km/h — 1 knot ≈ 1.852 km/h, not 1 km/h.
• Using a fixed Mach value for high-altitude calculations — the speed of sound decreases with altitude.

What is a knot?

A knot is one nautical mile per hour. 1 knot = 1.852 km/h = 1.151 mph. It is the standard speed unit in maritime and aviation navigation.

How fast is Mach 1?

At sea level and 15°C, Mach 1 ≈ 340.29 m/s ≈ 1,225 km/h ≈ 761 mph. The speed of sound decreases with altitude and temperature.