Mach Number Calculator

Mach Number Calculator: convert mach number instantly. Full formula, unit table, and worked example.

A speed converter switches between miles per hour (mph), kilometres per hour (km/h), metres per second (m/s), feet per second (ft/s), and knots (used in aviation and maritime contexts). Speed conversions are needed every time you cross an international border, work with physics equations, interpret athletic performance data, or follow aviation and marine navigation.

The US uses mph for road speed limits and car speedometers. Scientific calculations use m/s (SI unit). Aviation worldwide uses knots. Athletics uses m/s for short sprints and min/km or min/mile for distance running.

Enter the speed value and select the source unit (mph, km/h, m/s, knots, ft/s).
The converter shows equivalents in all units simultaneously.
For athletics: use the pace calculator (min/mile or min/km) which is more practical than speed for runners.

Speed conversion factors

1 mph = 1.60934 km/h = 0.44704 m/s = 1.46667 ft/s = 0.86898 knots

1 km/h = 0.62137 mph = 0.27778 m/s = 0.53996 knots

1 knot = 1.15078 mph = 1.852 km/h = 0.51444 m/s

1 m/s = 3.6 km/h = 2.23694 mph = 1.94384 knots = 3.28084 ft/s

Speed reference benchmarks

Common speed comparisons

Walking: 3–4 mph (4.8–6.4 km/h). Easy jogging: 5–6 mph (8–9.7 km/h). Cycling: 12–18 mph (19–29 km/h). US highway limit: 65–85 mph (105–137 km/h). Commercial aircraft cruise: 500–575 mph (805–925 km/h) = Mach 0.78–0.85. Speed of sound (at sea level, 20°C): 767 mph = 1,235 km/h = 340 m/s. Speed of light: 186,282 miles/s = 299,792 km/s.

Conversion tips and best practices

Quick mph to km/h: multiply by 1.6 (accurate to within 0.6%). Quick km/h to mph: multiply by 0.6 (slightly under — actual factor 0.6214).
For GPS navigation in countries with km/h limits: most modern GPS units and smartphones can toggle between mph and km/h in settings.
Wind speed is often reported in knots in aviation weather briefings — 1 knot = 1.15 mph; 50-knot winds = 57.5 mph = 92.6 km/h.
In physics, always use m/s for momentum, kinetic energy, and most SI calculations — convert from mph or km/h before computing.

Usain Bolt's world record 100m sprint peak speed was approximately 27.8 mph (44.7 km/h = 12.4 m/s) — recorded at the 2009 World Championships.
The fastest production car (Bugatti Chiron Super Sport 300+) has reached 304 mph (490 km/h).
The International Space Station orbits at approximately 17,500 mph (28,000 km/h = 7.67 km/s) to maintain orbit against Earth's gravity.

Common mistakes to avoid

Using km/h speed on mph roads or vice versa — a road sign showing 100 refers to 100 km/h (62 mph) in Canada/Europe, not 100 mph (161 km/h).
Confusing knots and mph in aviation — filing a flight plan in mph when the system expects knots causes errors in fuel calculations and arrival time estimates.
Forgetting to convert speed to m/s before plugging into physics equations — kinetic energy KE = ½mv² requires v in m/s for the answer to be in Joules.

Road speed limits are set by state and local authorities in the US. Always follow posted speed limits. Speed conversion data is based on exact SI definitions. Aviation speed usage must comply with applicable FAA and ICAO regulations.