Speed Converter
Convert speed between meters per second, km/h, mph, knots, and Mach. Includes real-world reference speeds for walking, driving, and sound.
Speed Converter
Calculator
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Formula: 1 m/s = 3.6 km/h = 2.237 mph = 3.281 ft/s = 1.944 knots
Worked example — 27.78 m/s = 100 km/h = 62.14 mph = 53.99 knots
Formula
1 m/s = 3.6 km/h = 2.237 mph = 3.281 ft/s = 1.944 knots
Meters per second is the SI unit for speed. Multiply by the appropriate factor for each target unit: 3.6 for km/h, 2.237 for mph, 3.281 for ft/s, 1.944 for knots, or divide by 343 (the approximate speed of sound at sea level) for a Mach number.
Worked Examples
Example 1: Highway Driving Speed
Problem:Convert 27.78 m/s, a common highway cruising speed, to km/h, mph, and knots.
Solution:km/h = 27.78 × 3.6 = 100.01 km/h mph = 27.78 × 2.23694 = 62.14 mph knots = 27.78 × 1.94384 = 53.99 knots
Result:27.78 m/s = 100 km/h = 62.14 mph = 53.99 knots
Example 2: Sprinter Top Speed
Problem:A sprinter reaches a peak speed of 12.4 m/s. Express this in km/h and mph.
Solution:km/h = 12.4 × 3.6 = 44.64 km/h mph = 12.4 × 2.23694 = 27.74 mph Mach = 12.4 / 343 = 0.0362
Result:12.4 m/s = 44.64 km/h = 27.74 mph (Mach 0.036)
Frequently Asked Questions
How do I convert km/h to m/s?
To convert km/h to m/s, divide by 3.6. For example, 100 km/h ÷ 3.6 = 27.78 m/s. This works because 1 km = 1,000 m and 1 hour = 3,600 seconds.
What is a knot and why is it used in aviation and sailing?
A knot is one nautical mile per hour, equal to 1.852 km/h or approximately 1.151 mph. It is used in navigation because nautical miles are based on the circumference of the Earth: one nautical mile equals one arcminute of latitude. This makes it easy to calculate distances directly from chart coordinates, which is why aviation and maritime navigation still rely on knots today.
What does Mach 1 mean and how does it vary?
Mach 1 is the speed of sound in air, approximately 343 m/s (1,235 km/h or 767 mph) at 20°C at sea level. The speed of sound decreases with altitude and temperature — at cruising altitude (~35,000 ft, -56°C), it drops to about 295 m/s. Supersonic aircraft are described in Mach numbers rather than absolute speed because aerodynamic effects depend on the ratio to local sound speed.
How do I convert miles per hour to feet per second?
Multiply mph by 1.46667 to get feet per second. Alternatively, remember that 60 mph equals exactly 88 feet per second — a handy rule of thumb. So 30 mph = 44 ft/s and 90 mph = 132 ft/s. This conversion is commonly used in traffic engineering, sports performance analysis, and stopping-distance calculations.
Why does m/s make sense as the base unit for a speed converter?
Meters per second is the SI derived unit for speed because it combines the two SI base units of length (meter) and time (second) with no additional conversion constant, which is why physics equations for velocity, momentum, and kinetic energy are written in m/s by default. Every other everyday speed unit — km/h, mph, knots, ft/s — is a regional or historical convenience unit that requires its own multiplication factor to reach m/s. Converting through m/s as the common base (rather than converting directly between, say, mph and knots) avoids compounding rounding errors across multiple conversion factors.
How fast do common things move, in m/s?
Concrete references help calibrate a speed value: an average walking pace is about 1.4 m/s (5 km/h), a casual jog is around 2.5-3 m/s, a professional sprinter peaks near 12 m/s (Usain Bolt's top speed was about 12.4 m/s), typical highway driving is 25-31 m/s (90-112 km/h), a commercial airliner cruises around 250 m/s, and sound travels at roughly 343 m/s at sea level. Comparing a calculated value to these benchmarks is a fast sanity check that a conversion has been entered correctly.
Why do wind speed and boat speed use knots instead of mph or km/h?
Knots remain the standard for maritime and aviation contexts because a nautical mile is defined relative to Earth's geometry — one nautical mile equals one minute of latitude — which lets navigators read distance and speed directly off latitude lines on a chart without a separate conversion step. This geometric convenience, established centuries before GPS, is why international aviation, shipping, and most weather services still report wind speed and vessel speed in knots even though those industries otherwise use metric units extensively.
What is the difference between speed and velocity?
Speed is a scalar: it states how fast something moves with no direction attached, and it is what every unit on this converter expresses. Velocity is a vector, combining that magnitude with a direction, so 20 m/s north and 20 m/s south are the same speed but opposite velocities. The distinction matters in physics because acceleration is a change in velocity, meaning an object moving at constant speed around a circle is still accelerating. For unit conversion the factors are identical either way; only the direction component is left out.
How do I turn a running pace in minutes per kilometer into m/s?
Convert the pace into seconds per kilometer, then divide 1,000 by that number. A 5:00 per kilometer pace is 300 seconds, so the speed is 1000/300 = 3.33 m/s, which is 12.0 km/h. Pace and speed are reciprocals of one another, so a given improvement in pace represents a larger change in m/s at fast speeds than at slow ones. For miles, divide 1,609.34 by the seconds per mile to get m/s.
What is the difference between ground speed and airspeed for an aircraft?
Airspeed is the aircraft's speed relative to the air mass it is flying through, while ground speed is its speed relative to the ground. The two differ by the wind component along the flight path: a jet with 450 knots true airspeed flying into a 50-knot headwind makes 400 knots over the ground, and with a 50-knot tailwind it makes 500 knots. Flight time depends on ground speed, whereas aerodynamic behaviour and Mach number depend on airspeed, which is why both are reported in knots and tracked separately.
References
Reviewed for accuracy by Manoj Kumar, Mathematics Educator · Editorial policy
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