Speed Converter
Convert speed units instantly—kilometers per hour (km/h), miles per hour (mph), meters per second (m/s), knots, and more. Enter a value, choose units, and get accurate results in seconds. Ideal for driving, travel, sports, and technical calculations. Free and easy to use.
Speed Converter
The Speed Converter converts between 11 speed units spanning everyday road speeds (km/h, mph), scientific and engineering speeds (m/s, ft/s, ft/min), maritime and aviation navigation (knots, nautical mph), and extreme reference speeds (Mach and speed of light). Select the From and To units, enter the value, and click Convert.
Speed units differ by country and industry. Road speeds in Europe and most of the world use km/h; the US and UK use mph. Aviation and maritime navigation worldwide use knots. Physics and engineering use m/s. Supersonic speeds use Mach number. Converting accurately between these systems is essential for travel planning, engineering, physics, and reading international specifications.
How to use the Speed Converter
- Enter the speed value to convert.
- Select the From unit — the unit your value is currently in (e.g. km/h, mph, m/s).
- Select the To unit — the unit you want to convert to.
- Click Convert. The result is displayed immediately.
- To convert to additional units, change the To dropdown and click Convert again.
All 11 units — values in m/s and typical contexts
| Unit | In m/s | Typical context |
| Everyday road and civil speeds | ||
| Kilometer/hour (km/h) | 0.27778 m/s | Road speed limits and vehicle speed in most countries worldwide. The standard unit for driving speed outside the US, UK, and a small number of other countries. A 100 km/h motorway speed limit = 62.1 mph = 27.78 m/s. |
| Mile (US)/hour (mph) | 0.44704 m/s | Road speed limits and vehicle speed in the US, UK, Liberia, and Myanmar. UK roads use mph for all speed limit signs. 60 mph = 96.56 km/h; 70 mph (UK motorway limit) = 112.65 km/h. |
| Mile (US)/minute | 26.8224 m/s | Rarely used in everyday contexts. Occasionally appears in race commentary or vehicle performance specifications. 1 mi/min = 60 mph = 96.56 km/h. |
| Mile (US)/second | 1,609.344 m/s | Used in some ballistics and projectile speed specifications. 1 mi/s = 3,600 mph = 5,793.6 km/h. A typical rifle bullet travels at approximately 0.5–1.5 mi/s (800–2,400 m/s). |
| Scientific / SI units | ||
| Meter/second (m/s) | 1 m/s | The SI base unit of speed. Used in physics, science, and engineering calculations. 1 m/s = 3.6 km/h = 2.237 mph. Wind speed is sometimes reported in m/s. The speed of sound at sea level is approximately 343 m/s. |
| Foot/second (ft/s) | 0.3048 m/s | US and UK engineering, ballistics, and fluid dynamics. 1 ft/s = 0.6818 mph = 1.0973 km/h. Muzzle velocity of firearms and projectile speeds are often specified in ft/s in the US. 1,000 ft/s = approximately 682 mph. |
| Foot/minute (ft/min) | 0.00508 m/s | HVAC air velocity in ducts and ventilation systems. Air velocity in building ventilation is commonly measured in feet per minute. Typical duct air velocity is 400–2,000 ft/min. Elevator speed in the US is specified in ft/min. |
| Navigation units | ||
| Knot (international, kn) | 0.51444 m/s | The standard speed unit for all maritime and aviation navigation globally. 1 knot = 1 international nautical mile per hour = 1.852 km/h = 1.151 mph. Air traffic control, pilot airspeed indicators, and maritime charts all use knots. A cruising commercial aircraft flies at approximately 450–500 knots; a modern container ship at 18–25 knots. |
| Mile (nautical)/hour | 0.51444 m/s | Numerically identical to knots — 1 nautical mile per hour = 1 knot. This entry uses 'nautical mile per hour' as the explicit unit name rather than the abbreviated 'knot'. The two are the same speed. |
| Relative and extreme speed units | ||
| Mach (at STP) | 340.29 m/s | Mach number is the ratio of an object's speed to the local speed of sound. Mach 1 at sea level standard conditions (STP: 15°C, 1 atm) ≈ 340.29 m/s = 1,225 km/h = 761.2 mph. At altitude, the speed of sound decreases: at cruising altitude (~35,000 ft, -56°C), the speed of sound is approximately 295 m/s (1,062 km/h), so Mach 1 there ≈ 1,062 km/h. Commercial aircraft cruise at approximately Mach 0.78–0.85. Concorde cruised at Mach 2.04. |
| Speed of light (c) | 299,792,458 m/s | The speed of light in a vacuum: exactly 299,792,458 m/s (approximately 300,000 km/s = 186,282 mi/s). This is a defined physical constant — the meter is now defined in terms of c. Light crosses the Earth (circumference ~40,075 km) approximately 7.5 times per second. Light takes approximately 8 minutes 20 seconds to travel from the Sun to Earth. Used in physics, relativity, and calculations involving electromagnetic radiation. |
Mach number — why it depends on temperature
Mach number is not a fixed speed — it is a ratio of an object's speed to the local speed of sound. The speed of sound varies with air temperature, so the same Mach number represents a different physical speed at different altitudes and conditions:
- At sea level, standard conditions (15°C, 1 atm): Mach 1 = approximately 340 m/s = 1,225 km/h = 761 mph.
- At cruising altitude (~35,000 feet, -56°C): the air is colder and thinner, and the speed of sound decreases to approximately 295 m/s = 1,062 km/h = 660 mph. A commercial aircraft flying at Mach 0.85 at this altitude is travelling at approximately 903 km/h (561 mph), not 1,041 km/h (the Mach 0.85 figure at sea level).
- This is why aircraft airspeed is specified in both indicated airspeed (IAS) and Mach number for high-altitude flight — the Mach number tells pilots how close they are to the speed of sound in the current air conditions.
The converter uses Mach at Standard Temperature and Pressure (STP: 15°C, 1 atm, sea level) as the reference: Mach 1 (STP) = 340.29 m/s = 1,225.08 km/h = 761.21 mph. For conversions involving aircraft at cruising altitude, use this value as an approximation — the actual Mach-to-km/h conversion at altitude will be different. For precise aircraft performance calculations, use the speed of sound at the specific altitude and temperature.
Knots — the universal navigation speed unit
A knot (kn or kt) is one international nautical mile per hour. 1 knot = 1.852 km/h = 1.151 mph = 0.5144 m/s. Knots are used universally in aviation and maritime navigation because the nautical mile is directly tied to Earth's geometry: 1 nautical mile = 1 minute of arc of latitude = 1,852 meters. This means a ship or aircraft travelling at 1 knot is covering 1 minute of arc per hour, which makes navigation calculations on a globe directly consistent with speed in knots.
The term 'knots' originates from the historical practice of measuring a ship's speed by throwing a knotted rope overboard and counting how many knots passed through a sailor's hands in a fixed time interval (using a 28-second sandglass). The spacing of the knots on the log line was calibrated so that the count directly gave the speed in nautical miles per hour.
It is correct to say a speed of '25 knots' — not '25 knots per hour'. A knot already means 'nautical miles per hour', so 'knots per hour' is a redundant and incorrect formulation. This is a common error in non-specialist writing and speech. The plural of knot as a speed unit is knots: a ship travelling at 20 nautical miles per hour has a speed of 20 knots.
Speed scale reference — familiar speeds in four units
The table below shows familiar reference speeds in km/h, mph, m/s, and knots to help build intuition and verify conversion results:
| Speed reference | km/h | mph | m/s | knots |
| Walking pace (brisk) | 6 | 3.7 | 1.67 | 3.24 |
| Cycling (recreational) | 20 | 12.4 | 5.56 | 10.8 |
| UK/US urban road limit | 48.3 | 30 | 13.4 | 26.1 |
| UK motorway / US freeway limit | 112.7 | 70 | 31.3 | 60.9 |
| German Autobahn (advisory) | 130 | 80.8 | 36.1 | 70.2 |
| Usain Bolt (100 m world record) | 37.6 | 23.4 | 10.44 | 20.3 |
| Speed of sound at sea level | 1,225 | 761.2 | 340.3 | 661.5 |
| Commercial jet (cruise) | 900 | 559 | 250 | 486 |
| Concorde (cruise) | 2,180 | 1,354 | 606 | 1,178 |
| SR-71 Blackbird (record) | 3,530 | 2,194 | 981 | 1,906 |
Usage limits
| Account type | Daily conversions |
| Guest | 25 per day |
| Registered | 100 per day |
Related tools
- Length Converter — convert kilometers, miles, nautical miles, meters, feet, and more. Use alongside the Speed Converter for distance calculations (distance = speed x time).
- Time Converter — convert seconds, minutes, hours, days, and more. Use with speed and distance for journey time calculations.
- Power Converter — convert watts, kilowatts, horsepower, and more. Power and speed are linked in vehicle performance (power = force x speed).
Frequently asked questions
How do I convert km/h to mph?
Multiply km/h by 0.621371 to get mph. To convert mph to km/h: multiply by 1.60934. Examples: 100 km/h x 0.621371 = 62.1 mph; 60 mph x 1.60934 = 96.6 km/h; 110 km/h = 68.4 mph; 70 mph (UK motorway limit) = 112.7 km/h. Quick approximation: km/h x 0.6 ≈ mph; mph x 1.6 ≈ km/h. The Fibonacci approximation from the length converter also works here: consecutive Fibonacci numbers (5/8, 8/13, 13/21) approximate the km/miles ratio to within 0.5%.
What is a knot and why is it used in aviation and maritime navigation?
A knot is one international nautical mile per hour = 1.852 km/h = 1.151 mph. It is the universal speed unit for aviation and maritime navigation because the nautical mile is defined by Earth's geometry: 1 nautical mile = 1 minute of arc of latitude. Navigating in nautical miles and knots makes calculations on a spherical globe directly consistent — a ship at 60 knots covers 1 degree of latitude per minute. All global air traffic control, commercial shipping, and military navigation use knots regardless of the country involved.
What does Mach 1 mean and how fast is it?
Mach 1 is the speed of sound in the current medium. At sea level standard conditions (15°C, 1 atm): Mach 1 = approximately 340 m/s = 1,225 km/h = 761 mph. Mach numbers below 1 are subsonic; above 1 are supersonic; above 5 are hypersonic. The speed of sound varies with temperature — at aircraft cruising altitude (~35,000 feet, -56°C), it decreases to approximately 295 m/s (1,062 km/h). Commercial jets cruise at approximately Mach 0.78–0.85. The Concorde cruised at Mach 2.04. The SR-71 Blackbird held the air-breathing aircraft speed record at approximately Mach 3.3.
How do I convert m/s to km/h?
Multiply m/s by 3.6 to get km/h. To convert km/h to m/s: divide by 3.6 (or multiply by 0.27778). This relationship comes from unit analysis: 1 m/s = 1 meter per second = 1,000 meters per 1,000 seconds = 1 km per (1000/3600) hours = 3.6 km/h. Examples: 10 m/s x 3.6 = 36 km/h; 100 km/h / 3.6 = 27.78 m/s. The quick check '1 m/s = 3.6 km/h' is one of the most useful mental shortcuts in physics.
What is the speed of light in km/h and mph?
The speed of light in a vacuum (c) = exactly 299,792,458 m/s = approximately 1,079,252,848 km/h (approximately 1.08 billion km/h) = approximately 670,616,629 mph (approximately 671 million mph). Light travels approximately 300,000 km per second. It takes light approximately 1.3 seconds to reach the Moon from Earth, approximately 8 minutes 20 seconds to travel from the Sun to Earth, and approximately 4.24 years to reach the nearest star (Proxima Centauri). The speed of light is a defined constant in SI — the meter is literally defined as the distance light travels in 1/299,792,458 of a second.
How fast is 100 km/h in mph and m/s?
100 km/h = 62.137 mph = 27.778 m/s = 53.996 knots. This is a common speed to check because 100 km/h is a standard motorway speed limit in many European countries, and 60 mph is an approximate mph equivalent that many drivers use informally. The exact figure is 62.137 mph — using 60 mph as an approximation underestimates by about 3.6%.
What is ft/min and when is it used?
Foot per minute (ft/min) is a speed unit used primarily in US HVAC engineering for air velocity in duct systems. Typical air velocity in building supply ducts is 400–2,000 ft/min (2–10 m/s). It is also used for elevator speed specifications in the US — a high-speed elevator may travel at 1,000–2,000 ft/min (5–10 m/s). Vertical speed in aviation (rate of climb or descent) is measured in feet per minute (fpm) worldwide — a standard commercial jet descent rate is approximately 1,500–2,500 fpm.
Is the Speed Converter free?
Yes. The converter is free within the daily usage limits shown above. Guest users can perform 25 conversions per day without creating an account. Registering a free ToolsPiNG account increases the daily limit to 100 conversions per day.