Speed Unit Converter - km/h, mph, knots Online Free
Whether you are a driver checking speed limits in the USA, a physics student converting meters per second, a naval captain calculating in knots, or an aviation enthusiast tracking the speed of sound, our calculator provides instant answers.
We support lightning-fast conversions between all global units (km/h, mph, m/s, knots, Mach). Our tool connects the worlds of road transport, science, seafaring, and aviation. Everything works online, for free, and without any installation.
Smart Calculations: Why Convert Speed Here?
Speed is relative, but fines are real. And physics calculations? They can be tricky. Our tool eliminates errors when multiplying by constants and offers:
- Real-time calculations: No waiting. As soon as you enter a value, you immediately see the conversion. Ideal when you need a quick response (e.g., when planning a route).
- Specialized units: Regular calculators stop at km/h. We go further. We support nautical knots for yachtsmen and Mach number for aviation.
- Scientific accuracy: Our algorithm precisely handles the relationships between imperial and metric units. The “Quick Overview” table will also show you less common data, such as feet per second (ft/s), which sports shooters or technicians might appreciate.
Comprehensive Overview: Understanding Speed Units
Every environment has its own “language” of speed. Here’s an overview of the units our converter handles and where you’ll encounter them.
| Unit | Abbreviation | Approximate Conversion (to km/h) | Where it is Used |
|---|---|---|---|
| Kilometer per hour | km/h | 1 km/h | Roads in Europe, car speedometers, general transport, cycling. |
| Mile per hour | mph | approx 1.61 km/h | Roads in the USA and UK. Watch out for confusion when driving abroad! |
| Meter per second | m/s | 3.6 km/h | Physics and Science. The base SI unit. Used for wind, ballistics, sprints. |
| Knot | kn | approx 1.85 km/h | Sea and Air. Shipping and aviation (navigation). Equivalent to 1 nautical mile per hour. |
| Foot per second | ft/s | approx 1.1 km/h | Ballistics, muzzle velocity of projectiles, technical calculations in the USA. |
| Mach | Ma | approx 1235 km/h (at sea level) | Supersonic aviation. Speed of sound. (Value is dependent on air temperature and pressure). |
Instructions: How to Use the Converter
Operation is simple, whether you’re doing homework or planning a voyage.
1. Enter the Value
Enter a number into the left field.
- Example from the image: You enter
100(e.g., the speed of a very fast car or a hurricane).
2. Select Units
- In the left menu, choose the input unit (e.g., “meter per second”).
- In the right menu, choose the target unit (e.g., “kilometer per hour”).
- The arrow button is for quick swapping (Swap).
3. Get a Comprehensive Overview
Besides the main result (in the example, you see that 100 m/s is exactly 360 km/h), look down at the “Quick Overview”. There you will find, for example, that this speed corresponds to approximately 0.3 Mach or 194 knots.
Common Mistakes: Why is 100 m/s not 100 km/h?
When converting speed, fundamental errors are often made, which can lead to incorrect school results or road fines.
The Trickiness of m/s vs. km/h (The 3.6 Rule) Many people think it’s enough to multiply by ten or a hundred.
- Reality: 1 hour has 3600 seconds, and 1 kilometer has 1000 meters.
- From this, the coefficient 3.6 is derived.
- If you want to convert m/s to km/h, you must multiply the value by 3.6. (Example: 10 m/s × 3.6 = 36 km/h).
- If you convert km/h to m/s, you must divide by 3.6.
- Our converter does this automatically, so you don’t have to remember this formula.
Beware of “Miles” (mph) In the USA and Great Britain, speedometers show mph.
- If you see a sign “50”, it doesn’t mean 50 km/h (which is slow city driving), but 50 mph, which is approximately 80 km/h.
- Unawareness of this conversion is a frequent cause of unintentional speeding (or, conversely, traffic impedance) by Czech drivers abroad.
Speed Facts: How Fast Does It Go?
For a better idea of what the numbers mean:
- 5 km/h: Average walking speed (approx 1.4 m/s).
- 50 km/h: Common urban speed limit (approx 13.9 m/s).
- 120-130 km/h: Highway speed limit (approx 33-36 m/s).
- 343 m/s (1235 km/h): Speed of sound in air (Mach 1).
- 27,000 km/h: Approximate speed of the ISS (International Space Station) in orbit.