Instantly convert between 27 speed units — metric, imperial, knots, Beaufort scale and run pace. Real-time results across all groups.
Speed is the rate at which an object covers distance over time. It is one of the most fundamental physical quantities, governing everything from everyday road limits to astronomical distances. The SI (International System of Units) defines metres per second (m/s) as the base unit. In everyday life, kilometres per hour (km/h) is dominant across Europe and most of the world, while miles per hour (mph) remains the standard in the United States and the United Kingdom. Mariners and aviators use knots (nautical miles per hour), and meteorologists sometimes express wind strength using the Beaufort scale.
This converter handles 27 units organised into four groups: Metric, Imperial/US, Other (knots, Beaufort, speed of light), and Run Pace. All conversions route through metres per second as the internal pivot. The Beaufort scale uses a non-linear power-law formula, and run pace units are the inverse of speed — a useful duality for athletes timing their kilometres or miles.
All linear units convert via a constant factor f (where 1 unit = f m/s). The general formula is:
Linear units (all except Beaufort and pace):
Beaufort scale (non-linear power law):
Run pace units (inverse of speed, where d is the distance in metres):
Where f_source is the number of metres per second in one source unit, and f_target is the same for the target unit. The converter first converts to m/s, then to the target unit.
The UK national speed limit on motorways is 70 mph, which equals approximately 112.7 km/h or 31.3 m/s. In nautical terms this is about 61.2 knots — far faster than any vessel. The limit was introduced in 1965 following a trial on the M1 motorway, and has remained unchanged since, making it a well-known conversion reference for British drivers.
Usain Bolt's 100 m world record of 9.58 s (set in Berlin, 2009) corresponds to an average speed of 10.44 m/s or 37.58 km/h. His peak speed during the race reached roughly 12.4 m/s (44.72 km/h). In running pace terms, that peak translates to approximately 2:14 min/km — a pace no marathon runner can sustain.
The speed of sound at sea level (20 °C dry air) is approximately 343 m/s or 1,235 km/h (Mach 1). The speed of light in vacuum is exactly 299,792,458 m/s ≈ 1,079,252,849 km/h — roughly 874,030 times faster than sound. A Beaufort 12 hurricane (≥32.7 m/s) represents barely 0.0001% of the speed of sound.
The ISS orbits Earth at approximately 7,660 m/s (27,576 km/h or 17,130 mph). In run pace units, this translates to about 0.13 seconds per kilometre — a distance a human runner takes 3–6 minutes to cover. The ISS completes one full orbit every 90 minutes, circling Earth roughly 15.5 times per day.
Enter the speed value in the input field. Positive numbers, decimals and very large values (e.g. fractions of the speed of light) are all supported.
Select the source unit from the dropdown. All 27 units are listed with full names and symbols, organised by group.
The converter converts your value to metres per second (m/s) using the unit's conversion factor (or the Beaufort power law, or the pace inverse formula).
Results are displayed in five sections: Key Units (m/s, km/h, mph, kn, ft/s), then expandable groups for Metric, Imperial/US, Other, and Run Pace.
All conversions update instantly as you type. Very large or very small numbers are shown in scientific notation for readability.
Quick mental shortcut: 1 mph ≈ 1.609 km/h. To roughly convert mph to km/h, multiply by 1.6 (exact: 1.60934). So 60 mph ≈ 96 km/h and 100 mph ≈ 160 km/h.
Knots to km/h: 1 knot = 1.852 km/h (exactly, by definition of the nautical mile). So a wind speed of 20 knots ≈ 37 km/h, and 50 knots ≈ 93 km/h.
Run pace conversion: to get min/km from km/h, divide 60 by the speed. A 10 km/h running pace equals 60/10 = 6:00 min/km. A 12 km/h pace equals 5:00 min/km.
Beaufort scale is approximate — it describes the observed effects of wind rather than an exact speed. Beaufort 8 (gale) corresponds to 17.2–20.7 m/s (62–74 km/h). Use it for rough estimation, not precision engineering.
The speed of light (c = 299,792,458 m/s) is a universal physical constant and the maximum speed in the universe. Velocities approach but never reach c. Use the 'c' unit to convert spacecraft or particle speeds as a fraction of light speed.
Speed is a scalar quantity — it describes how fast an object moves, without regard for direction. Velocity is a vector quantity — it describes speed in a specific direction. For conversions, only the magnitude (speed) matters. For example, a car travelling north at 60 mph and a car travelling south at 60 mph have the same speed but opposite velocities.
Run pace (minutes or seconds per kilometre/mile) is the inverse of speed. The faster you run, the fewer seconds you need per kilometre, so the pace number decreases. A pace of 5:00 min/km is faster than 6:00 min/km. When you increase speed in the converter, the pace values decrease. This is why athletes talk about 'running a faster pace' when the pace number is lower.
A knot is one nautical mile per hour. A nautical mile (1,852 m) is based on one minute of arc of latitude on the Earth's surface, making it a natural unit for maritime and aerial navigation. Sailors historically measured speed by throwing a log overboard attached to a rope with knots tied at regular intervals, counting the knots that passed through their hands in a fixed time — hence the name. Today, knots remain the standard in aviation and maritime contexts worldwide.
The Beaufort scale (0–12) was created by Admiral Francis Beaufort in 1805 to describe wind strength based on observable sea conditions. The modern empirical formula relating Beaufort number B to wind speed v in m/s is: v = 0.836 × B^1.5. This means Beaufort 0 is calm (< 0.3 m/s), Beaufort 6 is a strong breeze (10.8–13.8 m/s), and Beaufort 12 is a hurricane (≥32.7 m/s). The scale is non-linear — each unit represents a larger increase in actual wind speed.
No physical object with mass can reach or exceed the speed of light (c ≈ 3 × 10^8 m/s), according to Einstein's special theory of relativity. The converter allows mathematical input of such values for academic reference (e.g. theoretical tachyon speeds), but they have no physical meaning for classical objects. Massless particles like photons travel at exactly c in vacuum.
For scientific and engineering work, always use SI units. The SI base unit of speed is metres per second (m/s). It integrates cleanly with other SI units: kinetic energy uses kg·m²/s², force uses kg·m/s², and power uses kg·m²/s³. For aerodynamics and gas dynamics, Mach number (speed relative to local sound speed) is common. For particle physics, fractions of the speed of light (c) are standard.
All conversions use exact or standard-definition factors (e.g. 1 inch = 0.0254 m, 1 nautical mile = 1852 m exactly). The Beaufort formula is an empirical approximation. Run pace values are the mathematical inverse of speed and assume perfectly uniform motion.