About the Speed Converter
This converts a speed between the common units — kilometres per hour, miles per hour, metres per second, feet per second, and knots. Handy for reading a speed limit or vehicle speed in the other system, converting wind or boat speed in knots, or turning a physics value in metres per second into something more intuitive.
How it works
Each unit is defined relative to metres per second (m/s), the SI base; your value converts to m/s and then to the target unit. Key relationships:
- 1 km/h = 0.27778 m/s (divide km/h by 3.6 to get m/s).
- 1 mph = 1.609344 km/h (the same factor as miles to kilometres).
- 1 knot = 1.852 km/h (one nautical mile per hour), used for wind, sea and air speed.
So 100 km/h ≈ 62.1 mph ≈ 27.8 m/s ≈ 54 knots.
Assumptions and behaviour
- A knot is one nautical mile per hour (1.852 km/h), distinct from a statute mph.
- To go from km/h to m/s quickly, divide by 3.6; the tool does this precisely.
- Results show about 7 significant figures.
- The Swap button reverses the two units.
Limitations
- It converts a constant speed value between units; it doesn't work out speed from distance and time (divide distance by time first, then convert if needed).
- Knots aren't mph — don't mix them up when reading marine or aviation figures.
- Displayed values are rounded, so hand-chaining rounded figures can drift slightly.
Privacy
The conversion runs entirely in your browser. Nothing is uploaded or stored.
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