Speed Converter
Convert between km/h, mph, m/s, knots and the speed of light.
What the Speed Converter does
Speed is distance over time, so the conversion factor combines both. A knot is one nautical mile per hour, used in sailing and aviation. Mach numbers vary with air temperature — the value here is for sea level.
Formula
Convert to metre per second, then divide by the target unit's factorResult = Value × (from factor ÷ to factor)
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Value | number | Yes | — |
| From | one of 7 options | Yes | — |
| To | one of 7 options | Yes | — |
How to use it
- Choose From and To.
- Enter Value.
- Select Calculate.
Worked example
Convert 100 km/h to mph.
- Value
- 100
- From
- km/h
- To
- mph
100 × 0.621371 = 62.14 mph.
Frequently asked questions
Quick way to convert km/h to mph?
Multiply by 0.6 for a rough figure. 100 km/h ≈ 60 mph, close to the exact 62.14.
Why do ships and planes use knots?
One knot is one nautical mile per hour, and a nautical mile is one minute of latitude — which makes chart navigation arithmetic simple.