Speed

The Speed Converter handles the most common units for measuring how fast something is moving: kilometres per hour (km/h), miles per hour (mph), metres per second (m/s), knots (used in maritime and aviation), and Mach (the ratio of speed to the speed of sound).

Whether you are checking a foreign speedometer, converting a sailing speed, or sanity-checking how fast a passenger jet actually goes, this tool handles the math without you needing to remember the factors.

Units supported

• km/h — used for road speeds in most of the world.
• mph — used for road speeds in the US, UK, and a few other countries.
• m/s — the SI standard, used in physics and engineering.
• knots — nautical miles per hour, used in maritime and aviation.
• Mach — speed expressed as a multiple of the speed of sound (~343 m/s at sea level, 20°C).

Conversion factors

• 1 km/h = 0.621371 mph = 0.27778 m/s
• 1 mph = 1.609344 km/h = 0.44704 m/s
• 1 m/s = 3.6 km/h = 2.23694 mph
• 1 knot = 1.852 km/h = 1.15078 mph
• Mach 1 ≈ 1,234.8 km/h at sea level, 20°C (varies with altitude and temperature)

Worked examples

• A typical highway speed of 100 km/h is roughly 62.1 mph or 27.8 m/s.
• A cruising commercial jet at 900 km/h ≈ 559 mph ≈ 486 knots ≈ Mach 0.73.
• A sailboat doing 8 knots is moving at 14.8 km/h or 9.2 mph.

When this is useful

Driving abroad, reading aviation or maritime data, physics homework, sports performance tracking (running pace conversions), and any context where you need to compare speeds expressed in different units.

About Mach

Mach is not a fixed-length unit — the speed of sound depends on temperature and altitude. At sea level on a standard day it is about 343 m/s; at high altitude in cold air it can drop to around 295 m/s. The Mach value here uses the sea-level standard for everyday comparison.

Frequently asked questions

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