Speed Unit Conversion: mph, km/h and More
Speed units come up in driving, aviation, sailing, running, cycling, weather reports and physics. Whether you are reading a car speedometer, checking a weather forecast, following a race or working through a physics problem, you will encounter speed in different units.
This guide explains every common speed unit, gives you the exact conversion formulas and links to the free Speed Converter for instant results.
The Main Speed Units
| Miles per hour (mph) | Used in the US and UK for road speeds and wind speed. |
| Kilometres per hour (km/h) | Used in most countries for road speeds. |
| Metres per second (m/s) | The SI unit of speed. Used in science and physics. |
| Knots (kn or kt) | Used in aviation and maritime navigation. 1 knot = 1 nautical mile per hour. |
| Feet per second (ft/s) | Used occasionally in US engineering and ballistics. |
| Mach number | Ratio of speed to the speed of sound. Used in aviation for high-speed aircraft. |
mph to km/h Conversion
km/h = mph multiplied by 1.60934
mph = km/h multiplied by 0.62137
Example 1: Convert 60 mph to km/h
60 multiplied by 1.60934 = 96.56 km/h
Example 2: Convert 100 km/h to mph
100 multiplied by 0.62137 = 62.14 mph
Quick mental shortcut: multiply mph by 1.6 to get approximate km/h.
Speed Conversion Reference Table
| mph | km/h | m/s |
|---|---|---|
| 10 mph | 16.09 km/h | 4.47 m/s |
| 20 mph | 32.19 km/h | 8.94 m/s |
| 30 mph | 48.28 km/h | 13.41 m/s |
| 40 mph | 64.37 km/h | 17.88 m/s |
| 50 mph | 80.47 km/h | 22.35 m/s |
| 60 mph | 96.56 km/h | 26.82 m/s |
| 70 mph | 112.65 km/h | 31.29 m/s |
| 80 mph | 128.75 km/h | 35.76 m/s |
| 100 mph | 160.93 km/h | 44.70 m/s |
| 100 km/h | 62.14 mph | 27.78 m/s |
| 110 km/h | 68.35 mph | 30.56 m/s |
| 130 km/h | 80.78 mph | 36.11 m/s |
Knots: Aviation and Maritime Navigation
A knot is one nautical mile per hour. One nautical mile is 1,852 metres. Nautical miles and knots are used because one nautical mile equals one minute of latitude, which makes navigation calculations simpler.
Knot Conversions
1 knot = 1.852 km/h = 1.151 mph = 0.514 m/s
Example: A ship sailing at 20 knots
20 multiplied by 1.852 = 37.04 km/h
20 multiplied by 1.151 = 23.02 mph
Commercial Aircraft Cruise Speed
A typical airliner cruises at about 480 knots.
480 multiplied by 1.852 = 889 km/h (approximately 552 mph)
Common Speed Limits Around the World
| km/h | mph | Context |
|---|---|---|
| 30 km/h | 18.6 mph | Common residential and school zone limit |
| 50 km/h | 31.1 mph | Standard urban speed limit in most of Europe |
| 80 km/h | 49.7 mph | Rural roads in many countries |
| 100 km/h | 62.1 mph | Standard national speed limit in many countries |
| 120 km/h | 74.6 mph | Motorway limit in France, Italy and others |
| 70 mph | 112.7 km/h | UK motorway speed limit |
| 65 mph | 104.6 km/h | Common US interstate limit |
| 75 mph | 120.7 km/h | Some US western state highway limits |
Speed of Sound and Mach Numbers
At sea level and 15 degrees Celsius, the speed of sound is approximately 340 metres per second (1,225 km/h or 761 mph). The Mach number describes how fast something is moving relative to the speed of sound.
| Mach 1 | 340 m/s / 1,225 km/h / 761 mph (speed of sound at sea level) |
| Mach 0.85 | 289 m/s / 1,041 km/h / 647 mph (typical commercial airliner cruise) |
| Mach 2 | 680 m/s / 2,450 km/h / 1,522 mph (supersonic) |
| Mach 5 | 1,700 m/s / 6,125 km/h / 3,806 mph (hypersonic) |
Running and Cycling Pace
| Pace | km/h | mph and Context |
|---|---|---|
| 5 min/km | 12 km/h | 7.46 mph (good recreational running pace) |
| 6 min/km | 10 km/h | 6.21 mph (comfortable jogging pace) |
| 4 min/km | 15 km/h | 9.32 mph (fast club runner) |
| 25 km/h cycling | 25 km/h | 15.5 mph (moderate recreational cycling) |
| 35 km/h cycling | 35 km/h | 21.7 mph (sportive or road club cycling) |
Related Tools
- Speed Converter mph, km/h, knots, m/s, feet per second and more
- Length Converter for distance calculations that go alongside speed
- All Unit Converters browse all 74 converters on CalConvs
Frequently Asked Questions
How do I convert mph to km/h?
Multiply mph by 1.60934 to get km/h. For a quick mental estimate, multiply by 1.6. So 30 mph is about 48 km/h, 60 mph is about 96 km/h and 70 mph is about 112 km/h. To convert back from km/h to mph, multiply by 0.62137 or divide by 1.6 for an estimate.
What is 100 km/h in mph?
100 km/h equals 62.14 mph. This is just over 62 mph. For a mental estimate, multiply by 0.6 to get 60 mph. The exact answer is a little over 62. In countries where 100 km/h is the highway speed limit, this corresponds to roughly 62 miles per hour.
What is a knot in miles per hour?
One knot equals 1.15078 mph, or about 1.852 km/h. A knot is one nautical mile per hour. Nautical miles are slightly longer than regular land miles, 1,852 metres compared to 1,609 metres. Aviation and maritime navigation use knots because nautical miles align with the geometry of the Earth's coordinate system.
How fast is the speed of sound in mph?
The speed of sound at sea level and 15 degrees Celsius is approximately 761 mph (1,225 km/h or 340 metres per second). This is Mach 1. The speed of sound varies with temperature and altitude, at higher altitudes where the air is colder, the speed of sound decreases. At cruising altitude for commercial aircraft, the speed of sound is about 660 mph (1,062 km/h).