What are the most common speed units?

Common speed units: mph (miles per hour, US roads), km/h (kilometers per hour, most road signs worldwide), m/s (meters per second, scientific), knots (nautical miles per hour, aviation and maritime), ft/s (feet per second, some engineering uses). Mach numbers express speed as a multiple of the speed of sound (~343 m/s at sea level).

How do I convert mph to m/s?

Multiply mph by 0.44704 to get m/s. Examples: 30 mph = 13.41 m/s, 60 mph = 26.82 m/s, 100 mph = 44.7 m/s. Conversely, m/s x 2.237 = mph.

What is Mach 1 in mph and km/h?

Mach 1 (speed of sound at sea level, 15C) = approximately 767 mph = 1,235 km/h = 343 m/s. At high altitude (35,000 ft), air is colder and Mach 1 is lower: about 660 mph = 1,062 km/h = 295 m/s. The speed of sound varies with temperature and altitude.

What is 1 knot in mph and km/h?

1 knot = 1 nautical mile per hour = 1.15078 mph = 1.852 km/h. A nautical mile is 1,852 meters (6,076 feet), based on one minute of arc of latitude. Aircraft typically cruise at 450-500 knots (520-575 mph). Wind speeds in weather are often reported in knots.

Speed Converter

Convert between m/s, km/h, mph, ft/s, knots, Mach and more.

About Speed Units

Speed measures the distance traveled per unit of time. m/s is the SI unit. km/h and mph are used in everyday transport. Knots are used in aviation and maritime navigation. Mach is the ratio to the speed of sound (~340 m/s).

Quick Reference Table

Unit	In m/s
1 km/h	0.27778 m/s
1 mph	0.44704 m/s
1 knot	0.51444 m/s
Mach 1	340.29 m/s
1 ft/s	0.3048 m/s

Related Converters

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Speed Units Around the World

Road speeds in the US and UK use miles per hour (mph); most other countries use km/h. Aviation uses knots (1 knot = 1.852 km/h). Scientific calculations use m/s. Mach number expresses speed relative to the speed of sound (~343 m/s at sea level at 20 °C). Understanding conversions is essential when comparing vehicle specs from different markets.

Speed Conversion Quick Reference

mph	km/h	m/s	knots
30	48.3	13.4	26.1
60	96.6	26.8	52.1
100	160.9	44.7	86.9

Speed in Aviation and Maritime Navigation

Pilots and sailors use knots because nautical miles are based on the Earth's geometry (1 nautical mile = 1 arcminute of latitude = 1.852 km). This makes navigation charts and speed calculations consistent regardless of position on Earth. A commercial aircraft cruises at about 480 knots = 890 km/h. Container ships travel at 20–25 knots. Speed of sound at sea level is approximately 661 knots = 1,225 km/h = 340 m/s. Exceeding it produces a sonic boom from the shockwave created by compressed air.

Speed Units Across Transportation and Science

Speed is distance divided by time, and the unit chosen depends on context. Meters per second (m/s) is the SI unit, used in physics and engineering calculations. Kilometers per hour (km/h or kph) is the legal road-speed unit in most countries. Miles per hour (mph) is standard in the United States, United Kingdom, and a few other countries. Knots (nautical miles per hour) are used universally in maritime and aviation navigation because nautical miles correspond to arc-minutes of latitude, simplifying chart work. Feet per second (fps) appears in ballistics and some US engineering standards. Mach number expresses speed as a multiple of the local speed of sound (approximately 340 m/s at sea level, 20°C). Converting between these units is necessary when comparing international vehicle specifications, reading foreign road signs, or translating scientific results into engineering-friendly formats.

Speed Unit Conversion Reference Table

Unit	m/s	km/h	mph
1 m/s	1	3.600	2.237
1 km/h	0.2778	1	0.6214
1 mph	0.4470	1.6093	1
1 knot	0.5144	1.8520	1.1508
Mach 1 (sea level)	340.3	1225	761.2

Speed Contexts: Road, Rail, Air, and Sea

Different transport modes favor different speed units. Road vehicles use mph (US/UK) or kph (rest of world). Rail systems quote speeds in kph for international high-speed rail and mph for US Amtrak lines. Aircraft cruise speeds are stated in knots (kt) for ATC communication (1 kt = 1.852 kph = 1.150 mph), with airspeed indicators reading in knots. Ships use knots universally. Sound speed in air at sea level (approximately 340 m/s = 1225 kph = 761 mph) defines Mach 1. Firearms projectiles are measured in feet per second (fps) or meters per second (m/s). Satellite orbital speeds (~7,900 m/s) and escape velocity (~11,200 m/s) are in metric. Having a feel for multiple speed scales — and the ability to convert quickly — helps engineers, pilots, navigators, and scientists communicate across disciplines and international boundaries without misunderstanding.