Speed Converter Free Online
Convert between metric and imperial speed units instantly. Supports meters per second, kilometers per hour, miles per hour, feet per second, knots, and Mach number for aviation.
All Conversions
Pro — bulk batch conversion, API access, history & favorites
API access · Priority queue · Team workspace
How It Works
Enter a Value
Type the number you want to convert into the From input. The conversion runs as you type — no Convert button needed. Decimals and very small or very large numbers are supported via scientific notation.
Pick Source & Target Units
Use the two dropdowns to choose source (From) and destination (To) units. The result updates automatically. Use the swap button to flip the conversion direction in one click.
See All Conversions
Below the main result, the All Conversions panel shows your input value converted into every supported unit at once — perfect for comparing metric vs imperial side by side.
Speed Converter Features
Everyday Speed
km/h and mph for cars, bikes, and runners. 1 mph = 1.609 km/h exactly. Convert speed-limit signs across borders.
Marine Knots
Knot = 1 nautical mile per hour = 1.852 km/h exactly. Standard for ships, boats, and weather (wind speed).
Aviation Ready
Aircraft speed in knots, Mach number, and ft/s for airshow figures. Mach is given at sea level (343 m/s); true Mach varies with temperature and altitude.
Scientific m/s
m/s is the SI base unit. Used in physics, engineering, and ballistics. All other speeds derive from it.
Live Conversion
Result updates as you type. Useful for converting wind speed (mph → knots) or sprint pace (m/s → km/h) on the fly.
100% Private
All math runs in your browser. No telemetry, no tracking, safe for any use case.
Free vs Pro
| Feature | Free | Pro |
|---|---|---|
| All 6 speed units | ||
| Live conversion | ||
| All-units result table | ||
| Bulk CSV / Excel conversion | — | |
| REST API access | — | |
| Custom precision settings | — |
Frequently Asked Questions
1 knot = 1.15078 mph = 1.852 km/h exactly. The knot is defined as one nautical mile per hour, and a nautical mile equals one minute of arc of latitude (1852 m).
Mach 1 is the speed of sound. At sea level in dry air at 20 °C it is about 343 m/s (1235 km/h, 767 mph, 667 knots). Mach varies with air density: at 11 km altitude it drops to about 295 m/s (663 mph). Our calculator uses the sea-level value.
Divide km/h by 3.6 to get m/s. Example: 90 km/h ÷ 3.6 = 25 m/s. Multiply by 3.6 to go the other way.
The US, UK (road signs), and a few other countries use mph for road speed. The rest of the world uses km/h. Aviation worldwide uses knots, regardless of country.
For min/km ↔ min/mi pace conversion use our dedicated Pace Converter. This tool converts steady speed (the inverse of pace).