Last updated: May 2026
Convert between km/h, mph, m/s, knots, and fps instantly — with common speed reference table.
Convert between km/h, m/s, mph, knots, and fps
Common Speed References
| km/h | mph | Context |
|---|---|---|
| 30 km/h | 18.6 mph | Residential speed limit (EU) |
| 50 km/h | 31.1 mph | Urban speed limit |
| 100 km/h | 62.1 mph | Highway limit (many EU countries) |
| 120 km/h | 74.6 mph | German autobahn advisory |
| 1 knot | 1.852 km/h | Nautical / aviation speed |
Other Unit Converters
Speed has more units in active daily use than almost any other measurement type: km/h for driving in most countries, mph in the US and UK, m/s in physics and science, and knots in aviation and maritime navigation. Each field has its own default, and you'll cross between them constantly when traveling, analyzing performance data, or reading technical specs.
The underlying relationship: speed = distance ÷ time. Converting speed means converting the distance unit while keeping the time unit fixed. Knots are the exception — one knot equals one nautical mile per hour, where a nautical mile (1,852 meters) is based on the circumference of the Earth.
| From | To | Multiply By | Common Use Case |
|---|---|---|---|
| km/h | mph | 0.621371 | International driving speed limits |
| mph | km/h | 1.60934 | US car specs → European road signs |
| m/s | km/h | 3.6 | Physics problems → everyday speed |
| km/h | m/s | 0.277778 | ÷ 3.6 |
| knots | km/h | 1.852 | Aviation/sailing → road context |
| knots | mph | 1.15078 | Nautical to land speed |
| mph | m/s | 0.44704 | Speed → physics units |
How fast is 100 km/h in mph?
100 km/h = 62.14 mph. A useful reference: 100 km/h is just over 62 mph. And 60 mph = 96.56 km/h — just barely under 100 km/h. Germany's autobahn recommended speed of 130 km/h equals about 81 mph.
What is a knot in terms of km/h?
One knot equals 1.852 km/h or 1.151 mph. A knot is one nautical mile per hour, and a nautical mile (1,852 meters) is based on one minute of arc of latitude on the Earth's surface. Pilots and sailors use knots because they relate directly to coordinates on a navigation chart.
Is there a quick mental math trick for km/h to mph?
Multiply by 5, then divide by 8. Since 1 km is very close to 5/8 of a mile, this is nearly exact. Example: 80 km/h → 80 × 5 = 400 ÷ 8 = 50 mph. Actual answer: 49.7 mph. The error is under 1%, which is good enough for any practical estimate.
How fast is the speed of sound in km/h and mph?
The speed of sound in air at 20°C is approximately 343 m/s, which equals 1,235 km/h or 767 mph. This is called Mach 1. At higher altitudes where air is colder and thinner, the speed of sound decreases — commercial jets cruise at roughly Mach 0.85, or about 900 km/h at altitude.
Why do pilots use knots instead of km/h or mph?
Navigation. A nautical mile corresponds to one minute of latitude on the globe, so speed in knots maps directly onto chart coordinates. Flying at 450 knots means covering 450 nautical miles per hour — and those nautical miles align with latitude/longitude positions. This simplifies flight planning and reduces the chance of navigation errors.