Speed Unit Converter
Type a value once and instantly see it in km/h, mph, m/s, ft/s, knots, Mach number and fractions of c. Handy for converting overseas speed limits, reading marine or aviation GPS, physics and sports-science homework, or comparing wind speeds, vehicle top speeds and ballistic muzzle velocities.
Please enter a valid number
Live value in every speed unit
Tip: 1 km/h ≈ 0.621 mph, 1 knot = 1.852 km/h (exact), Mach 1 varies with air temperature — default here is the ICAO standard atmosphere at sea level (15 °C, 340.29 m/s).
- km/h Road speed limits in most of the world (EU, Asia, AU)
- mph US / UK road signs and motorsport top speeds
- m/s SI base — physics formulas, engineering, kinematics
- kn Marine and aviation (1 nautical mile / h = 1.852 km/h)
- ft/s Ballistics, baseball pitches, archery, US civil engineering
- Mach Aircraft / supersonic flight (ICAO ISA sea-level @ 15 °C)
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Formula
value (m/s) = input × factor km/h → m/s : ÷ 3.6 mph → m/s : × 0.44704 ft/s → m/s : × 0.3048 knot → m/s : × 1852 / 3600 Mach → m/s : × 340.29 (ICAO standard sea level, 15 °C) c → m/s : × 299 792 458
- · 1 km/h = 1000 m / 3600 s (exact SI derived); 1 mph = 1.609344 km/h (exact, from the 1959 international yard / mile of 1609.344 m).
- · 1 knot = 1 nautical mile / hour = 1.852 km/h, where 1 nm = 1852 m by the 1929 BIPM agreement. Used worldwide by shipping and ATC.
- · Mach 1 depends on temperature and air density; this tool uses the ICAO standard atmosphere at sea level, 15 °C ≈ 340.29 m/s. At 11 km cruise altitude it is closer to 295 m/s.
- · The speed of light c = 299 792 458 m/s is exact — since 1983 the metre is defined from c. Everyday speeds expressed in fractions of c use scientific notation.
- · Most of the world signs speed limits in km/h; the US, UK and a handful of Caribbean nations still use mph — the ratio is ≈ 1.609.
Frequently asked
How many km/h is 60 mph?
60 mph = 96.5606 km/h (exact: 60 × 1.609344). The American 0-60 mph benchmark roughly tracks the European 0-100 km/h figure since 60 mph ≈ 96.56 km/h, but the two are not interchangeable when comparing manufacturer specs.
How fast is 1 knot in km/h and mph?
1 knot = 1 nautical mile per hour = 1.852 km/h ≈ 1.151 mph (both ratios are exact, anchored on the 1929 international nautical mile of 1852 m). Cargo ships cruise at 20-25 knots, a Cessna 172 around 100-120 knots, and a Boeing 777 about 480 knots.
Why does Mach 1 not have a fixed value?
The Mach number is the ratio of an object’s speed to the *local* speed of sound, and the speed of sound = √(γ·R·T) scales with the square root of absolute temperature. At 15 °C sea level it is 340.29 m/s; at the −56.5 °C stratosphere it drops to 295 m/s. So an airliner cruising at Mach 0.85 covers fewer km/h aloft than at the runway. This tool fixes Mach to the ICAO sea-level value for everyday comparisons.
Any everyday speed benchmarks for context?
Walking ≈ 5 km/h (1.4 m/s); casual cycling 15 km/h, race 40 km/h; Usain Bolt’s 100 m peak ≈ 44 km/h (12.2 m/s); motorway 100-120 km/h; hurricane-force wind ≥ 118 km/h; airliner cruise ≈ 870 km/h (Mach 0.82); Earth around the Sun ≈ 107 000 km/h; Sun around the Milky Way centre ≈ 828 000 km/h; speed of light 1 079 252 848 km/h.
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