mph to km/h Converter — Copy Any Unit Instantly
Type into whichever of the five boxes you already know and the rest recalculate instantly, each with its own copy button
Five boxes — m/s, km/h, mph, knots, and Mach — and you type into whichever one you already know; the rest recalculate the moment you do. Each box carries its own copy button, so you can grab just the unit you need rather than a whole block of text: handy for renting a car abroad, checking an aviation figure, or pasting one number into a spreadsheet. Reference constants for the speed of light, the speed of sound, highway speed limits, and Earth's escape velocity load with a single tap. Everything is computed in your browser and never sent to a server.
🔒 Everything runs 100% in your browser. Your files and input are never uploaded to any server.
How to use
- Type your value into the unit you already know (for example, mph)
- The remaining m/s, km/h, knots, and Mach values are calculated and displayed automatically
- Tap a reference button — speed of light, speed of sound, highway speed limit — to load that value instantly
- Use the copy button next to any result to send that unit's value to your clipboard
FAQ
- How is the Mach value calculated?
- Mach 1 is set to roughly 343 m/s, the speed of sound in dry air at 20°C (68°F).
- What is a knot based on?
- One knot is a speed of one nautical mile (1,852 m) per hour, and it's the standard unit in aviation and at sea.
- Are the speeds I enter stored on a server?
- No — every conversion is calculated inside your browser, and nothing is sent to a server.