Speed Converter
Convert between meters per second, kilometers per hour, miles per hour, knots, feet per second, Mach, and the speed of light, with every unit updating live as you type.
Common Speed Conversions
- 100 km/h ≈ 62.14 mph
- 60 mph ≈ 96.56 km/h
- 1 m/s = 3.6 km/h
- 1 knot = 1.852 km/h
- 1 mph = 0.44704 m/s
- Mach 1 ≈ 1,225 km/h (at sea level)
- The speed of light ≈ 1.08 billion km/h
Understanding Speed Units
Meters per second is the SI unit of speed and the base for scientific work, while kilometers per hour is what most of the world uses on road signs and in everyday conversation. Miles per hour is the imperial/US customary equivalent, standard on US and UK roads. Knots — nautical miles per hour — are used at sea and in the air, because a nautical mile is tied directly to a minute of latitude, making it convenient for navigation calculations that are done in degrees and minutes rather than kilometers.
Mach 1 is the local speed of sound, which isn't a fixed number — it depends on the temperature and density of the air (or other medium) it's traveling through, so 'Mach 1' is faster at sea level than at high altitude. This converter uses the standard sea-level reference value of 340.3 m/s (ISA conditions, 15°C) for its Mach conversions; real aircraft Mach readings vary with actual altitude and temperature. The speed of light in a vacuum, by contrast, is a true physical constant — exactly 299,792,458 meters per second by definition — included here to put everyday speeds in cosmic perspective.
Disclaimer: This converter is provided for general informational and reference purposes only. For applications where precision matters — medical dosing, engineering, construction, or legal and regulatory submissions — verify the result independently or consult a qualified professional.
Frequently Asked Questions
About this calculator
This speed converter lets you enter a value in any of 7 units and see it instantly converted to all the others — from meters per second up to the speed of light, including knots for marine and air navigation and Mach for aviation. It covers the metric system, the imperial/US customary system, and specialty units used in transport and physics, so you don't need to remember conversion factors or do the math by hand.
- 7 speed units at once — Meters per second, kilometers per hour, miles per hour, knots, feet per second, Mach, and the speed of light, all converted simultaneously.
- Live conversion — Type a value into any unit and every other field updates instantly — no need to click a button or pick a 'from' and 'to' unit.
- Aviation and marine units included — Knots and Mach are built in alongside everyday road-speed units, useful for aviation, marine navigation, and flight-related calculations.
- Speed of light for perspective — Converts everyday speeds against the speed of light in a vacuum, an exact physical constant, to put fast speeds in cosmic context.
- Quick reference table — Common conversions (km/h to mph, m/s to km/h, and more) are listed for fast lookup without typing anything.