Speed Converter
Convert between m/s, km/h, mph, knots, and Mach.
How to Use Speed Converter
- 1Enter a speed value
- 2Select the source unit
- 3See all other unit equivalents instantly
About Speed Converter
The Speed Converter converts between all common speed and velocity units: meters per second, kilometers per hour, miles per hour, knots, feet per second, and Mach number. Enter any speed value in any unit and see all other equivalents instantly.
The converter covers everyday transportation speeds (km/h, mph), aviation and maritime units (knots), scientific units (m/s), and the dramatic Mach scale based on the speed of sound. Mach conversions use the standard sea-level speed of sound (343 m/s at 20°C).
All processing runs locally in your browser with no server calls. The converter is equally useful for students doing physics problems, pilots checking speed equivalents, travelers comparing international speed limits, and engineers working on aerodynamics.
Key Features of Speed Converter
- Convert between m/s, km/h, mph, knots, ft/s, and Mach
- Mach conversions based on standard sea-level speed of sound (343 m/s)
- All equivalents shown simultaneously in one view
- High-precision conversion factors for engineering and science use
- Accepts decimal values for fractional speed inputs
- Instant results as you type
- Useful for physics, aviation, maritime, and transportation contexts
- Fully browser-based with no server dependency
Supported Formats
Input Formats
Output Formats
Mach 1 = 343 m/s at 20°C sea level. 1 knot = 1 nautical mile per hour = 1.852 km/h. 1 mph = 1.60934 km/h.
Examples
Convert km/h to mph for a speed limit
Convert a 120 km/h motorway speed limit to miles per hour.
Input
120 km/h
Output
74.56 mph | 33.33 m/s | 64.80 knots | Mach 0.097
Convert Mach to km/h for aircraft speed
Convert a Mach 2 aircraft speed to km/h.
Input
Mach 2
Output
2,469.6 km/h | 1,534.4 mph | 1,332.9 knots
Common Use Cases
- Converting speed limits between mph and km/h when driving internationally
- Understanding aircraft speeds in both Mach and km/h
- Converting ship speeds between knots and km/h for navigation
- Physics homework converting m/s to mph or km/h
- Comparing sports performance speeds in different units
- Aerodynamics calculations involving Mach number and m/s
Troubleshooting
Assuming Mach 1 is always the same speed
Solution
The speed of sound varies with altitude and temperature. Mach 1 at sea level (20°C) = 343 m/s, but at cruising altitude it is approximately 295 m/s. This converter uses sea-level standard conditions.
Confusing knots with km/h
Solution
1 knot = 1 nautical mile per hour = 1.852 km/h. Knots and km/h are different units. A ship doing 10 knots is traveling at 18.52 km/h, not 10 km/h.
Using mph when knots are needed for maritime or aviation contexts
Solution
Aviation and maritime navigation use knots as the standard. Always verify which speed unit is expected in your context before converting.
Frequently Asked Questions
What Mach number is used for the speed of sound?
Mach 1 = 343 m/s, which is the speed of sound in dry air at 20°C at sea level. The speed of sound decreases with altitude and temperature.
What is a knot?
A knot is one nautical mile per hour, equal to 1.852 km/h or 1.151 mph. It is the standard speed unit in aviation and maritime navigation.
How fast is 100 km/h in mph?
100 km/h = 62.14 mph. The common approximation is that 100 km/h is roughly 62 mph.
What is Mach 2?
Mach 2 is twice the speed of sound, approximately 686 m/s = 2,469 km/h = 1,534 mph at sea level (20°C).
Can I convert very high speeds like satellites?
Yes. The converter handles very high speeds accurately. For example, low Earth orbit velocity is approximately 7,800 m/s = Mach 22.7.
Is m/s or km/h used in physics?
Physics typically uses SI units, so meters per second (m/s) is the standard. The converter makes it easy to work with m/s while also checking the km/h or mph equivalent.
Why are two different "mph" units not shown?
Miles per hour here refers to statute miles (land miles), which is the standard for road use in the US and UK. Nautical miles per hour is shown separately as knots.
Is my data private?
Yes. All conversions run entirely in your browser. No values are transmitted to any server.