Speed Converter

Convert between km/h, mph, m/s, and knots

All conversions use metres per second (m/s) as a canonical intermediate value, which avoids rounding errors when chaining between units. The results shown maintain full floating-point precision internally and are formatted for readability.

Units supported

• Kilometres per hour (km/h) — the road speed unit used internationally.
• Miles per hour (mph) — used on roads in the UK and US.
• Metres per second (m/s) — the SI base unit; used in scientific and engineering contexts, and for wind speeds.
• Knots (kn) — 1 nautical mile per hour; the standard unit for maritime and aviation speed, and shown on many GPS devices.

Reference values

• 1 mph = 1.609344 km/h exactly (the statute mile is defined as 1,609.344 m)
• 30 mph = 48.28 km/h · 50 km/h = 31.07 mph
• 70 mph = 112.65 km/h — the UK motorway limit
• 130 km/h = 80.78 mph — a common European motorway limit