Speed & Velocity Converter

Convert between km/h, mph, m/s, knots, feet per second, and Mach number — for driving, running, sailing, aviation, and physics.

Speed & Velocity

mph, km/h, knots, mach

From

Result

3.6

1 m/s = 3.6 km/h

Popular conversions

What Is a Speed Converter?

A speed converter translates how fast something moves from one unit to another — kilometres per hour to miles per hour, metres per second to knots, and so on. Speed is distance divided by time, so every speed unit pairs a length unit with a time unit; converting means reconciling both at once. The physical speed never changes, only the number and label: 100 km/h, 62 mph, 27.8 m/s, and 54 knots all describe the same motion.

This converter routes through metres per second, the SI unit of speed, using exact ratios. It also covers knots (nautical miles per hour, the marine and aviation standard) and Mach number (speed relative to the local speed of sound), so a single figure can be read in whichever unit a driver, sailor, pilot, or physicist needs.

This is one category of the full Unit Converter — pair it with our percentage calculator or scientific calculator for related everyday maths.

How Speed Conversion Works

Everything routes through m/s

Each unit has a fixed metres-per-second factor. The converter turns your input into m/s, then projects it into every other speed unit so all outputs agree.

km/h and m/s differ by 3.6

Because there are 3,600 seconds in an hour and 1,000 m in a km, 1 m/s = 3.6 km/h. Dividing by 3.6 is the most common speed conversion in physics.

Knots use the nautical mile

One knot is one nautical mile (1,852 m) per hour ≈ 1.852 km/h ≈ 1.151 mph. Used at sea and in the air because it ties to latitude.

Mach is relative to sound

Mach number is speed divided by the local speed of sound (~343 m/s at 20 °C). Because the speed of sound falls with temperature, the same Mach is a slower true speed at altitude.

Core Speed Conversion Factors

Multiply to reach metres per second; divide to come back. Watch the 3.6 factor between km/h and m/s.

km/h → m/s

÷ 3.6

One m/s is 3.6 km/h. Divide km/h by 3.6 to get the SI speed used in physics.

mph → km/h

× 1.609344

One mile per hour is 1.609344 km/h, since the mile is 1.609344 km.

Knots → mph

× 1.150779

One knot is 1.150779 mph — a nautical mile is about 15% longer than a statute mile.

How to Use the Speed Converter

1
Enter the speed
Type the speed you want to convert — a vehicle's speed, a wind reading, a running pace, an aircraft's airspeed.
2
Choose the 'from' unit
Pick km/h, mph, m/s, knots, ft/s, or Mach as your starting unit.
3
Choose the 'to' unit
Select the target unit, or swap the two to reverse the conversion.
4
Read all units at once
The all-units table shows the speed in every unit simultaneously — handy when an airspeed in knots needs a mph or km/h sense-check.

Key Speed Concepts

Metre per second

The SI unit of speed, used in physics and engineering. Highway driving is about 30 m/s; a fast sprinter peaks near 12 m/s.

Knot

One nautical mile per hour (1.852 km/h). The marine and aviation standard, because a nautical mile equals one minute of latitude on a chart.

Mach number

Speed as a multiple of the local speed of sound. Mach 1 is ~343 m/s at sea level but slower at altitude, where the air is colder.

Speed vs velocity

Speed is a magnitude; velocity adds direction. Converters work with speed (the number), while velocity matters for navigation and physics vectors.

Real-World Speed Conversions

🚗

Driving abroad

A 100 km/h motorway limit is 62 mph; a 30 mph zone is 48 km/h. Drivers crossing between metric and US regions convert limits constantly.

✈️

Airspeed

A 480-knot cruise is 552 mph or 888 km/h. Pilots read knots, but passengers picture mph or km/h.

🌬️

Wind speed

A 50-knot gale is 58 mph or 93 km/h. Meteorologists report wind in knots, then forecasts convert for the public.

🏃

Running pace

A 10 km/h jog is 6.2 mph or 2.78 m/s. Treadmills and running apps switch between km/h, mph, and pace-per-distance.

🚢

Ship speed

A 22-knot container ship is 25 mph or 41 km/h — slow by road standards but efficient across an ocean.

🔬

Physics problems

A 90 km/h car is 25 m/s, the SI speed needed for kinetic energy and momentum. Dividing km/h by 3.6 is a constant in mechanics.

Best Practices for Speed Conversion

✓Divide km/h by 3.6 for m/s. The 3.6 factor between km/h and m/s is the most-forgotten step in physics. Always convert speeds to m/s before using SI formulas.
✓Confirm whether a speed is in knots. A knot is ~1.15 mph, not 1. Reading an airspeed in knots as mph understates the true speed by about 15%.
✓Treat Mach as temperature-dependent. Mach 1 is the local speed of sound, which falls with temperature. Use the sea-level 343 m/s only when that assumption holds.
✓Use m/s for any calculation. Kinetic energy, momentum, and kinematics all expect SI speed. Convert local units to m/s at the start, then convert the result back for display.
✓Sanity-check against a benchmark. Highway driving is ~30 m/s, a jet cruise ~250 m/s. If a converted value is far off a familiar benchmark, suspect a unit mix-up.

Common Speed Conversion Mistakes

Forgetting the 3.6 factor

Converting km/h to m/s without dividing by 3.6 — or dividing by 10 instead — is one of the most common physics-homework errors.

Reading knots as mph

A knot is about 1.15 mph. Treating an airspeed indicator's knots as mph understates the real speed by roughly 15%.

Assuming Mach is a fixed speed

Mach 1 changes with air temperature. Using 343 m/s at high altitude, where sound travels slower, overstates the true speed of a given Mach number.

Confusing speed with velocity

Speed is just a magnitude; velocity includes direction. For navigation and vector physics you need velocity, not a scalar speed conversion.

Why Speed Conversion Matters

Speed limits, airspeeds, wind warnings, running paces, and physics problems all live in different units depending on the field and the country — and the moment those worlds meet, a conversion is required. Misreading knots as mph, or forgetting the 3.6 factor between km/h and m/s, has shown up in everything from navigation slips to failed engineering calculations.

Because each speed unit pairs a length with a time, a sloppy conversion compounds two ratios at once. A converter that routes through metres per second with exact factors — and keeps knots and Mach straight — lets a driver, sailor, pilot, athlete, or student move a single physical speed cleanly between whatever units the task demands.

Built for drivers, runners, cyclists, sailors, pilots, meteorologists, and physics students converting between km/h, mph, m/s, and knots.

Linear unit factors follow the BIPM SI brochure, the NIST Guide to the SI, and ISO 80000. Currency rates load live from open.er-api.com; crypto prices from CoinGecko. See our methodology and editorial policy. Educational only — not certified for regulated trading, settlement, medical, or aerospace use.

Speed Converter FAQs

Divide kilometres per hour by 1.609344 to get miles per hour. So 100 km/h = 62.14 mph, and 60 mph = 96.56 km/h. The factor comes from the mile being exactly 1.609344 km, so the conversion is exact.

Divide by 3.6, because 1 m/s = 3.6 km/h (there are 3,600 seconds in an hour and 1,000 metres in a kilometre). So 90 km/h = 25 m/s. Multiply m/s by 3.6 to go back. Forgetting this 3.6 factor is one of the most common speed-conversion errors.

One knot equals about 1.151 mph or exactly 1.852 km/h. A knot is one nautical mile per hour, and the nautical mile (1,852 m) is roughly 15% longer than the statute mile used by mph. So a 200-knot aircraft is travelling about 230 mph.

Mach 1 is the speed of sound, about 767 mph (343 m/s) in dry air at 20 °C at sea level. But the speed of sound falls with temperature, so at a jet's cruise altitude Mach 1 is closer to 660 mph. Mach is a ratio to the local speed of sound, not a fixed speed.

Because one nautical mile equals one minute of latitude, which makes navigation on a chart simple — a knot (one nautical mile per hour) ties speed directly to position. mph and km/h, based on land miles and kilometres, don't have that clean relationship to latitude.

It uses exact unit definitions (mile = 1,609.344 m, nautical mile = 1,852 m, foot = 0.3048 m, Mach 1 = 343 m/s at 20 °C) and routes every conversion through metres per second at full precision, so the result is exact to your input precision.