Speed Converter

Reviewed by the CalculatorHub team, edited by James Graham. NIST-defined conversion factors. Last verified 14 June 2026.

Speed measurements are fundamental to transportation, physics, and practical navigation, yet different contexts and countries use different units. The metric system standardizes on metres per second for scientific work and kilometres per hour for everyday road speeds, the latter being used in most countries worldwide. The United States uses miles per hour for road travel, with feet per second common in engineering contexts. Maritime and aviation industries use knots, defined as nautical miles per hour, because this unit relates directly to latitude and longitude on a globe. For transonic and supersonic speeds, aircraft speed is often expressed in Mach numbers, where Mach 1 is the speed of sound, approximately 343 metres per second at sea level in standard conditions. Modern conversion factors are NIST-defined with precision: 1 mile per hour equals exactly 0.44704 metres per second, 1 knot equals 0.514444 metres per second. Converting between speed units is essential when reading international road signs, understanding aircraft performance, comparing maritime speeds, or working with physics problems in different unit systems. This calculator displays seven common speed units: metres per second, kilometres per hour, miles per hour, knots, feet per second, centimetres per second, and Mach. Enter a value in any field and all others update instantly.