What are the speed conversion formulas?

To convert km/h to mph: multiply by 0.621371. To convert km/h to m/s: divide by 3.6. To convert km/h to knots: multiply by 0.539957. To convert mph to km/h: multiply by 1.609344. To convert m/s to km/h: multiply by 3.6. To convert knots to km/h: multiply by 1.852.

What is the difference between km/h and mph?

Kilometers per hour (km/h) is the metric unit used worldwide for road speeds and weather. Miles per hour (mph) is used primarily in the United States and United Kingdom. 1 mph equals 1.609344 km/h, meaning 60 mph equals approximately 97 km/h.

What is a knot and where is it used?

A knot equals one nautical mile per hour (1.852 km/h or 1.151 mph). It is the standard unit for maritime navigation and aviation because nautical miles relate directly to Earth's latitude (1 nautical mile = 1 minute of latitude). Wind speeds, ship speeds, and aircraft speeds commonly use knots.

Why is m/s used in science?

Meters per second (m/s) is the SI derived unit for speed and velocity. It integrates directly with other SI units (meters for distance, seconds for time) making physics calculations consistent. Force (Newtons), acceleration (m/s²), and energy (Joules) all use m/s as the base speed unit.

What is the speed of sound in different units?

At sea level and 20°C (68°F), the speed of sound (Mach 1) equals approximately 343 m/s, 1235 km/h, 767 mph, or 667 knots. This varies with temperature and altitude—sound travels faster in warmer air and slower at higher altitudes where air is thinner.

How do I convert Mach number to speed?

Mach number is the ratio of object speed to the speed of sound. Mach 2 means twice the speed of sound. To convert: Speed = Mach × speed of sound. At standard conditions: Mach 1 ≈ 343 m/s ≈ 1235 km/h ≈ 767 mph ≈ 667 knots. Multiply the Mach number by these values.

Speed Converter

Convert between kilometers per hour, miles per hour, meters per second, and knots with precise conversion factors.

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Value

Result

km/h:

mph:

m/s:

knots:

About Speed Converter

This speed converter transforms values between four common speed units: kilometers per hour (km/h), miles per hour (mph), meters per second (m/s), and knots (kt). The tool uses exact conversion factors defined by international standards for accurate results in navigation, aviation, automotive, and scientific applications.

It is useful for travel planning, aviation navigation, maritime operations, sports performance analysis, physics calculations, engineering specifications, weather reporting (wind speeds), and comparing speed limits across countries using different measurement systems.

Speed Unit Conversion Factors

These exact conversion factors are used for all calculations:

Base Conversions (to m/s):
  1 km/h = 0.2777778 m/s  (exactly 1000/3600)
  1 mph  = 0.44704 m/s    (exactly defined)
  1 m/s  = 1 m/s          (base unit)
  1 knot = 0.514444 m/s   (exactly 1852/3600)

Conversion Formulas:
  km/h → mph:   multiply by 0.621371
  km/h → m/s:   divide by 3.6
  km/h → knots: multiply by 0.539957

  mph → km/h:   multiply by 1.609344
  mph → m/s:    multiply by 0.44704
  mph → knots:  multiply by 0.868976

  m/s → km/h:   multiply by 3.6
  m/s → mph:    multiply by 2.236936
  m/s → knots:  multiply by 1.943844

  knots → km/h: multiply by 1.852
  knots → mph:  multiply by 1.150779
  knots → m/s:  multiply by 0.514444

Speed Unit Comparison

Unit	Symbol	System	Primary Usage
Kilometers per hour	km/h, kmph	Metric (SI derived)	Road signs, weather, most countries
Miles per hour	mph, mi/h	Imperial/US Customary	USA, UK road speeds, speed limits
Meters per second	m/s, m·s⁻¹	SI (Scientific)	Physics, engineering, science
Knots	kt, kn	Nautical/Aviation	Maritime, aviation, meteorology

Common Speed Reference Table

Scenario	km/h	mph	m/s	knots
Walking speed	5	3.1	1.4	2.7
Running (recreational)	10	6.2	2.8	5.4
Cycling (leisure)	15	9.3	4.2	8.1
Urban speed limit	50	31	13.9	27
Highway speed (Europe)	130	81	36.1	70
Highway speed (USA)	120	75	33.3	65
Train (intercity)	200	124	55.6	108
Speed of sound (Mach 1)	1235	767	343	667

Aviation Speed Reference

Aircraft Typical Speeds:

Commercial Jet (cruise):
  900 km/h = 560 mph = 486 knots = 250 m/s

Regional Turboprop:
  500 km/h = 310 mph = 270 knots = 139 m/s

General Aviation (Cessna 172):
  230 km/h = 140 mph = 124 knots = 64 m/s

Helicopter (typical):
  250 km/h = 155 mph = 135 knots = 69 m/s

Fighter Jet (supersonic):
  Mach 2 = 2470 km/h = 1535 mph = 1334 knots = 686 m/s

Takeoff Speeds:
  Boeing 737: 250-280 km/h (135-150 knots)
  Airbus A320: 260-280 km/h (140-150 knots)
  Cessna 172: 100-110 km/h (55-60 knots)

Landing Speeds:
  Boeing 737: 230-250 km/h (125-135 knots)
  Airbus A320: 240-260 km/h (130-140 knots)

Maritime Speed Reference

Vessel Typical Speeds:

Container Ship:
  35-45 km/h = 19-24 knots

Cruise Ship:
  37-46 km/h = 20-25 knots

Ferry:
  40-65 km/h = 22-35 knots

Speedboat:
  80-160 km/h = 43-86 knots

Naval Destroyer:
  55-60 km/h = 30-32 knots

Submarine (submerged):
  65-80 km/h = 35-43 knots

Wind Speed Categories (Beaufort Scale):
  Calm (Force 0): < 1 knot
  Light Air (Force 1): 1-3 knots
  Gentle Breeze (Force 3): 7-10 knots
  Moderate Gale (Force 5): 17-21 knots
  Strong Gale (Force 9): 41-47 knots
  Hurricane (Force 12): > 64 knots

Speed Conversion Examples

Example 1: Convert 100 km/h to mph
  mph = 100 × 0.621371
  mph = 62.14
  Answer: 100 km/h = 62.14 mph

Example 2: Convert 60 mph to km/h
  km/h = 60 × 1.609344
  km/h = 96.56
  Answer: 60 mph = 96.56 km/h

Example 3: Convert 50 knots to km/h
  km/h = 50 × 1.852
  km/h = 92.6
  Answer: 50 knots = 92.6 km/h

Example 4: Convert 10 m/s to km/h
  km/h = 10 × 3.6
  km/h = 36
  Answer: 10 m/s = 36 km/h

Example 5: Convert Mach 2 to km/h
  km/h = 2 × 1235 (at sea level)
  km/h = 2470
  Answer: Mach 2 ≈ 2470 km/h

World Speed Limit Comparison

Country	Urban (km/h)	Rural (km/h)	Highway (km/h)
Germany (Autobahn)	50	100	No limit* (130 advised)
France	50	80-90	130
United Kingdom	48 (30 mph)	97 (60 mph)	113 (70 mph)
United States	40-72 (25-45 mph)	89-105 (55-65 mph)	89-137 (55-85 mph)
Japan	40-50	50-60	100
Australia	50-60	100-110	110-130

*Germany has a recommended speed (Richtgeschwindigkeit) of 130 km/h but no mandatory limit on many Autobahn sections.

Unit History and Origins

Kilometers per hour (km/h):
  - Introduced with the metric system (1790s, France)
  - Kilometer defined as 1/10,000 of Earth's quadrant
  - Now defined as exactly 1000 meters per 3600 seconds
  - Adopted worldwide for road transport

Miles per hour (mph):
  - Mile originates from Roman "mille passus" (1000 paces)
  - Statute mile defined as 5,280 feet (1593, England)
  - mph became standard with railway development
  - Still used in USA, UK, and some Commonwealth nations

Meters per second (m/s):
  - SI derived unit, defined in 1960
  - Base unit for all scientific speed measurements
  - Integrates with Newton's laws and energy equations
  - Used universally in physics and engineering

Knots:
  - Named after the "chip log" method (17th century)
  - Sailors counted knots in a rope over 28 seconds
  - 1 knot = 1 nautical mile per hour
  - Nautical mile = 1 minute of latitude (1852 m exactly)

Speed in Physics

Speed and velocity are fundamental in physics equations:

Basic Kinematics:
  speed = distance / time
  v = d / t

  acceleration = change in velocity / time
  a = Δv / Δt

Newton's Second Law:
  F = ma (force = mass × acceleration)

Kinetic Energy:
  KE = ½mv² (requires m/s for Joules)

Momentum:
  p = mv (momentum = mass × velocity)

Wave Speed:
  v = fλ (frequency × wavelength)

Special Relativity:
  c = 299,792,458 m/s (speed of light)
  E = mc² (mass-energy equivalence)

Escape Velocity (Earth):
  vₑ = 11.2 km/s = 40,320 km/h = 25,054 mph

Frequently Asked Questions

What are the speed conversion formulas?: To convert km/h to mph: multiply by 0.621371. To convert km/h to m/s: divide by 3.6. To convert km/h to knots: multiply by 0.539957. To convert mph to km/h: multiply by 1.609344. To convert m/s to km/h: multiply by 3.6. To convert knots to km/h: multiply by 1.852.
What is the difference between km/h and mph?: Kilometers per hour (km/h) is the metric unit used worldwide for road speeds and weather. Miles per hour (mph) is used primarily in the United States and United Kingdom. 1 mph equals 1.609344 km/h, meaning 60 mph equals approximately 97 km/h.
What is a knot and where is it used?: A knot equals one nautical mile per hour (1.852 km/h or 1.151 mph). It is the standard unit for maritime navigation and aviation because nautical miles relate directly to Earth's latitude (1 nautical mile = 1 minute of latitude). Wind speeds, ship speeds, and aircraft speeds commonly use knots.
Why is m/s used in science?: Meters per second (m/s) is the SI derived unit for speed and velocity. It integrates directly with other SI units (meters for distance, seconds for time) making physics calculations consistent. Force (Newtons), acceleration (m/s²), and energy (Joules) all use m/s as the base speed unit.
What is the speed of sound in different units?: At sea level and 20°C (68°F), the speed of sound (Mach 1) equals approximately 343 m/s, 1235 km/h, 767 mph, or 667 knots. This varies with temperature and altitude—sound travels faster in warmer air and slower at higher altitudes where air is thinner.
How do I convert Mach number to speed?: Mach number is the ratio of object speed to the speed of sound. Mach 2 means twice the speed of sound. To convert: Speed = Mach × speed of sound. At standard conditions: Mach 1 ≈ 343 m/s ≈ 1235 km/h ≈ 767 mph ≈ 667 knots. Multiply the Mach number by these values.