Speed Converter

Road speeds by country

The United States and the United Kingdom sign roads in mph; Canada, Australia, India and most other countries use km/h. Common limits translate as 30 mph ≈ 48 km/h, 60 mph ≈ 97 km/h and 100 km/h ≈ 62 mph.

Speed unit definitions

meter per second (m/s)

The meter per second is the SI unit of speed. Walking is about 1.4 m/s, a sprinter about 10 m/s and sound in air about 343 m/s; multiply by 3.6 for km/h.

kilometer per hour (km/h)

Kilometres per hour is the road speed unit in Canada, Australia, India, Europe and most of the world. Highway limits are typically 100–130 km/h.

mile per hour (mph)

Miles per hour is the road speed unit in the United States and the United Kingdom. 60 mph is exactly 96.56064 km/h.

foot per second (ft/s)

Feet per second is used in US engineering, ballistics and physics problems. 88 ft/s is exactly 60 mph, and sound in air travels about 1125 ft/s.

knot (kn)

A knot is one nautical mile per hour. Ships, aircraft and marine weather use knots because a nautical mile is one minute of latitude.

Popular speed conversions

• meter per second to kilometer per hour
• kilometer per hour to meter per second
• kilometer per hour to mile per hour
• mile per hour to kilometer per hour
• knot to kilometer per hour
• knot to mile per hour

Related converters

• Length Converter – m, km, cm, mm, µm, ft, in, mi, yd, nmi
• Time Converter – ms, s, min, h, day
• Fuel Economy Converter – mpg (US, UK), L/100 km, km/L
• Printable speed conversion chart – print, PDF or PNG
• miles to kilometers (distance)
• face velocity and airflow converter (fpm, m/s)
• Centripetal Force Calculator – Mass, speed and radius → centripetal force and acceleration; or solve for any one of them.
• Speed Distance Time Calculator – Any two of speed, distance and time → the third, with pace per km and per mile.
• Acceleration Calculator – Initial and final velocity and time → acceleration; or solve for any of the four.
• Equations of Motion (SUVAT) Calculator – Any three of displacement, initial and final velocity, acceleration and time → the other two.
• Free Fall Calculator – Height or fall time → the other, plus impact speed, on Earth or any g.
• Projectile Motion Calculator – Launch speed, angle and height → range, maximum height, flight time and impact velocity.
• Kinetic Energy Calculator – Mass and speed → kinetic energy; or the speed or mass for a given energy.
• Momentum Calculator – Mass and velocity → momentum; or the mass or velocity for a given momentum.
• Escape Velocity Calculator – A planet (or any mass and radius) → escape velocity, surface orbit speed and surface gravity.
• Orbital Velocity Calculator – A body and an altitude → orbital speed, period and orbit radius.
• Wave Speed Calculator – Any two of wave speed, frequency and wavelength → the third, plus the period.
• de Broglie Wavelength Calculator – A particle and its speed, energy or accelerating voltage → its matter wavelength.
• Airspeed Calculator – One airspeed (CAS, EAS, TAS or Mach) and altitude → all the others.
• Mach Number Calculator – Speed and altitude (or temperature) → speed of sound, Mach number and flow regime.
• Lift Equation Calculator – Density, airspeed, wing area and C_L → lift; or solve for any one of them.
• Stall Speed Calculator – Mass, wing area, C_L,max and density → stall speed, manoeuvring speed and reference speeds.
• Turn Performance Calculator – Airspeed and bank angle → turn radius, rate, load factor and time for a full circle.
• Rate of Climb Calculator – Thrust, drag, airspeed and mass → rate of climb, climb angle and excess power.
• Glide Ratio Calculator – L/D and height (and speed) → glide distance, glide angle, sink rate and time.
• Hohmann Transfer Calculator – Central body and two circular orbit altitudes → Δv for each burn, total Δv and transfer time.
• Elliptical Orbit Calculator – Central body, periapsis and apoapsis → period, eccentricity, speeds and orbital energy.
• Boundary Layer Calculator – Free-stream speed, distance and viscosity → boundary-layer thicknesses and skin friction.
• Pitot Tube Calculator – Pitot and static pressures → airspeed (low speed) or Mach number (subsonic and supersonic).
• Rocket Equation Calculator – Specific impulse and mass ratio → Δv; or the mass, propellant or Isp needed for a Δv.
• Jet Engine Thrust Calculator – Air mass flow, fuel–air ratio, flight and exhaust speeds (and bypass) → thrust, TSFC and efficiencies.

Sources

• The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures.
• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology.

Last reviewed: 2026-10-15.