Speed Converter
Convert speed units instantly — km/h, mph, m/s, knots, Mach and more — with a live conversion table. Free, no signup.
Speed Converter Tool
Full Conversion Table
| Enter a value above to see conversions. |
Real-World Speed Reference
How to Use the Speed Converter
Enter your speed value
Type any numeric speed into the left input field. The converter accepts whole numbers and decimals. You can enter values as large as the speed of light (299,792,458 m/s) or as small as a snail's crawl.
Select your source unit
Choose the unit you are converting from using the dropdown below the value field. Options include km/h, mph, m/s, ft/s, knots, Mach (sea level, 20°C), and c (speed of light).
Choose your target unit
Select the unit you want to convert to using the right dropdown. The result updates immediately. Use the ⇄ swap button to reverse the conversion direction in one click.
See the full conversion table
Below the converter, the full table shows your value converted to all seven speed units at once. The real-world reference scale shows where your speed falls relative to everyday benchmarks — from walking pace to the sound barrier.
Speed Units — Why the World Still Can't Agree
km/h vs mph: Why the World Is Still Divided
The metric system was formalised in France in the late 18th century, and the International System of Units (SI) adopted kilometres per hour as the standard unit for road speed. Yet adoption was never universal. Most of the world now signs road speeds in km/h; the United States and the United Kingdom are the best-known exceptions, still posting limits in miles per hour.
In Southeast Asia, the transition to metric was completed decades ago. Malaysia and Singapore adopted the metric system fully in the 1970s, and road speed limits across the region are expressed in km/h. Singapore's expressways — the Pan-Island Expressway (PIE), the Central Expressway (CTE), the Ayer Rajah Expressway (AYE) — all post limits in km/h, typically 90 km/h for urban expressways. Malaysians colloquially refer to highway speeds as "100 kilo" meaning 100 km/h. Australia completed its metric conversion in 1974, and all Australian road signs display km/h.
The United Kingdom presents a curious hybrid: metric units are used for almost everything else, but British road signs still show distances in miles and speed limits in miles per hour.
Knots and Naval Speed — A Standard That Never Changed
A knot is defined as one nautical mile per hour, and a nautical mile is exactly 1,852 metres — corresponding to one arc-minute of latitude on the Earth's surface. This elegant connection to the geometry of the globe made knots invaluable to navigators long before GPS existed: a ship knowing its speed in knots could directly calculate its position on a nautical chart without any unit conversion.
Aviation adopted knots from maritime tradition, and the relationship has proven so useful that neither industry has ever seriously attempted to convert to km/h. Singapore's Changi Airport — one of the world's busiest — operates entirely on the knot standard for air traffic control. When a Singapore Airlines Airbus A380 lands at Changi, its approach speed of roughly 140 knots (about 259 km/h) is communicated in knots between the flight crew and ATC. The same is true at Seletar Airport and Paya Lebar Air Base.
"Singapore's Changi Airport is one of the busiest in the world — and every single aircraft landing and taking off has its speed measured in knots, not km/h, by ATC."
Singapore is one of the world's busiest container ports, so vessel speed is a constant operational concern. Container ships entering the Malacca and Singapore Straits operate under strict speed guidelines measured in knots, and maritime pilots boarding vessels at the Eastern and Western Anchorages communicate entirely in nautical units. The Vessel Traffic Information System (VTIS) operated by the Maritime and Port Authority of Singapore (MPA) tracks all ships in knots.
Sound Barrier and Mach Numbers — From Theory to Paya Lebar
Ernst Mach (1838–1916) was an Austrian physicist and philosopher who studied the behaviour of projectiles and gas at high velocities. The Mach number — the ratio of an object's speed to the local speed of sound — was named in his honour. Mach 1, the speed of sound, is approximately 1,235 km/h (343 m/s) at sea level at 20°C, but it varies significantly with altitude and temperature: at the cruising altitude of a commercial jet (around 35,000 feet), where temperatures fall to around −57°C, the speed of sound drops to roughly 1,062 km/h (295 m/s).
The sound barrier was first broken on 14 October 1947 by USAF test pilot Chuck Yeager in the Bell X-1 aircraft over the Mojave Desert, reaching Mach 1.06. Since then, supersonic flight has become routine for military aircraft. The Republic of Singapore Air Force (RSAF) flies supersonic fighters such as the F-15SG Eagle and the F-16C/D Fighting Falcon. Military supersonic operations in Singapore are conducted over the sea or during overseas training deployments, as supersonic flight over populated land is prohibited due to the sonic boom — the shockwave that produces a sharp thunderclap audible on the ground.
The Concorde, the retired Anglo-French supersonic airliner, cruised at Mach 2.04 (approximately 2,179 km/h), cutting the transatlantic crossing time to under four hours. It did fly to Singapore: from December 1977, British Airways and Singapore Airlines jointly ran a London–Bahrain–Singapore Concorde service, using an aircraft painted in Singapore Airlines colours on one side and British Airways colours on the other. Objections from Malaysia halted it after three return flights; it resumed in 1979 on a route avoiding Malaysian airspace and ended in November 1980.
A knot is an arc-minute, and sound slows down when it gets cold
One knot equals exactly 1,852 metres per hour — the length of one arc-minute of latitude on Earth's surface.
The speed of sound at sea level, 20°C is 1,235 km/h (343 m/s). At cruise altitude (−57°C) it drops to around 1,062 km/h.
The speed of light in a vacuum is 299,792,458 m/s — about 1.08 billion km/h. Nothing with mass can reach it.
Chuck Yeager first broke the sound barrier on 14 October 1947 in the Bell X-1 rocket plane over California's Mojave Desert.
Usain Bolt's maximum recorded sprint speed was 44.72 km/h (27.8 mph) during the 2009 World Championships 100 m final.
Singapore's Mass Rapid Transit (MRT) trains have a maximum design speed of around 90 km/h on the North–South and East–West Lines.
Formula 1 cars can reach top speeds of around 370–380 km/h on the longest straights, though average race speeds are 200–230 km/h.
Earth orbits the Sun at roughly 107,000 km/h (29.8 km/s) — about Mach 87 at sea-level sound speed.
Escape velocity from Earth's surface is 40,270 km/h (11.19 km/s) — the minimum speed needed to break free of Earth's gravity.
Mach number varies with temperature. At −57°C (cruise altitude), Mach 1 is roughly 1,062 km/h — 173 km/h slower than at 20°C sea level.
Frequently Asked Questions
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To convert km/h to mph, multiply by 0.621371. So 100 km/h × 0.621371 = 62.14 mph. Alternatively, divide km/h by 1.60934. This tool does it instantly for any value.
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A knot is one nautical mile per hour. One nautical mile is exactly 1,852 metres, corresponding to one arc-minute of latitude on Earth. So 1 knot = 1.852 km/h = 1.151 mph. Knots are used in aviation and maritime navigation worldwide, including at Singapore's Changi Airport and by the MPA for vessel traffic.
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Mach 1 at sea level and 20°C is approximately 1,235 km/h (343 m/s or 767 mph). This tool uses the sea-level 20°C value. The actual speed of sound changes with temperature and altitude — at 35,000 ft (−57°C), Mach 1 is roughly 1,062 km/h.
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Yes. The speed of sound depends primarily on air temperature, not altitude directly. At sea level (20°C) it is 343 m/s. At 10,000 m cruise altitude (−50°C) it falls to about 299 m/s. This is why an aircraft's Mach number can be higher at altitude even though its true airspeed in km/h may be similar to lower altitudes.
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Divide 60 by your pace in min/km. So a 5:00 min/km pace = 60 ÷ 5 = 12 km/h. A 6:00 min/km pace = 10 km/h. This tool handles the km/h side; for pace-to-speed conversion use our dedicated Running Pace Calculator.
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Nautical miles and knots are directly tied to Earth's geographic coordinate system — one nautical mile equals one arc-minute of latitude. This makes position calculation from speed and heading seamless on nautical charts. The system predates the metric system and was already the global standard when ICAO (aviation) and IMO (maritime) established their international conventions. No international body has found sufficient reason to change.
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The speed of light in a vacuum is 299,792,458 m/s, which equals approximately 1,079,252,849 km/h (about 1.08 billion km/h). Light travels from Earth to the Moon (384,400 km) in about 1.28 seconds.
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The North–South and East–West MRT Lines use Kawasaki/Siemens C151/C151B/C151C rolling stock with a maximum design speed of around 90 km/h. The Thomson–East Coast Line uses Alstom Metropolis trains with a similar top speed. The actual average speed over a journey is much lower, because trains slow down and stop at every station.
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Yes. km/h (kilometres per hour) and kph are the same unit, just different abbreviations. The SI standard abbreviation is km/h. In everyday speech, "kph" is common in Malaysia and Singapore. This tool uses km/h throughout.
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No. A real Mach number depends on the speed of sound where the aircraft is, and that falls as the air gets colder. This converter uses one fixed value, 343 m/s (about 1,235 km/h), the speed of sound in dry air at sea level and 20 °C. The International Standard Atmosphere (ISO 2533) assumes 15 °C at sea level, where sound travels at about 340 m/s, and at airliner cruising altitude it is nearer 295 m/s. Treat Mach results here as a sea-level, 20 °C conversion. All conversions run in your browser.
Method & sources
How it computes
Every unit converts through metres per second: km/h ÷ 3.6, mph × 0.44704, ft/s × 0.3048, knots × 0.514444 (1,852 m ÷ 3,600 s), Mach × 343 (speed of sound in dry air at 20 °C, sea level), c × 299,792,458. Value × its factor gives m/s; dividing by the target factor gives the result, shown to 6 significant figures. Mach is a ratio to a fixed 343 m/s, not to the local speed of sound.
What this tool implements
- Exact definitions: mile = 1,609.344 m and foot = 0.3048 m (international yard and pound agreement, 1959; NIST SP 811 B.8), nautical mile = 1,852 m exactly and knot = 1,852 m per hour (BIPM SI Brochure, non-SI units accepted for use), c = 299,792,458 m/s exactly (the SI definition of the metre).
- Mach uses 343 m/s (dry air, 20 °C, sea level). The ISO/ICAO standard atmosphere gives 340.3 m/s at 15 °C; the page states the assumption and that the speed of sound falls with temperature.
- Results are displayed to 6 significant figures; rounding is presentational only.
Sources
- NIST Special Publication 811, Appendix B.8 — conversion factors: foot 0.3048 m; mile 1.609 344 km; knot 0.514 444 m/s; mile per hour 0.447 04 m/s. https://www.nist.gov/pml/special-publication-811/nist-guide-si-ap…
- BIPM. The International System of Units (SI Brochure), 9th edition (2019) — the metre defined by fixing c = 299 792 458 m/s; nautical mile and knot among non-SI units accepted for use with the SI. https://www.bipm.org/en/publications/si-brochure
- ISO 2533:1975 Standard Atmosphere — sea-level temperature 15 °C and speed of sound 340.294 m/s, the reference against which the tool's 20 °C / 343 m/s convention is stated.
What can make this go out of date
- none at runtime — every factor is an exact definition except Mach, which is a stated convention
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