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Speed & Velocity Converter

Convert speed between m/s, km/h, mph, knots, ft/s, ft/min and Mach — all units shown at once, with a sea-level Mach note.

Mach uses the sea-level ISA speed of sound (340.29 m/s); it decreases with altitude.

About this tool

The Speed & Velocity Converter turns one speed into every common unit at once: metres per second, kilometres per hour, miles per hour, knots, feet per second, feet per minute and Mach number. Enter a value, pick the source unit, and the whole grid updates instantly.

Conversion is linear with metres per second as the base unit. Each unit stores how many of it equal one m/s, derived from the exact definitions 1 mph = 1609.344/3600 = 0.44704 m/s, 1 knot = 1852/3600 = 0.514444… m/s and 1 ft/s = 0.3048 m/s. Your value is converted to m/s (value ÷ source factor) and then multiplied by each target factor, so results stay exact.

Mach is included as a sea-level approximation using the ISA speed of sound, 340.29 m/s, so Mach 1 ≈ 1225 km/h ≈ 761 mph. The true speed of sound falls with altitude and temperature, so treat Mach here as a standard sea-level reference. All conversion runs locally in your browser with vanilla JavaScript — no uploads, works offline.

Frequently asked questions

Which speed units are supported?
Metres per second (m/s), kilometres per hour (km/h), miles per hour (mph), knots, feet per second (ft/s), feet per minute (ft/min) and Mach number at sea level.
How is Mach calculated here?
Mach is speed divided by the sea-level standard speed of sound, 340.29 m/s (ISA, 15 °C). So Mach 1 ≈ 1225 km/h. Because the speed of sound drops with altitude and temperature, this is a sea-level approximation, not the local Mach at cruising altitude.
What is a knot?
A knot is one nautical mile per hour, exactly 1852/3600 = 0.514444… m/s (≈1.852 km/h or ≈1.151 mph). It is the standard speed unit in aviation and marine navigation.
Are the mph and knot factors exact?
Yes. They come from exact length definitions: 1 mph = 0.44704 m/s and 1 knot = 0.5144444… m/s. Only the Mach factor is an approximation, because it depends on the assumed sea-level speed of sound.

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