Speed Converter

Free Online Speed Converter

This speed converter instantly converts between meters per second (m/s), kilometers per hour (km/h), miles per hour (mph), feet per second (ft/s), and knots (kn). It works as a km/h to mph converter, mph to km/h calculator, m/s to km/h converter, knots to mph converter, and ft/s to m/s converter all in one tool, so you never need to remember individual conversion formulas or search for a separate calculator for each unit pair.

Whether you're a student solving physics problems on velocity and motion, a driver or traveler comparing speed limits between countries that use km/h and mph, a runner or cyclist tracking pace, a pilot or sailor working with knots and airspeed, or a meteorologist reporting wind speed, this speed conversion calculator gives you an instant, accurate result along with a visual diagram and complete step-by-step working.

How to Use This Speed Conversion Calculator

Using this online speed converter takes only three quick steps. Enter the numeric value you want to convert, choose the unit you're converting from in the "From" dropdown, and choose the unit you want to convert to in the "To" dropdown — the converted result updates instantly as you type. Use the swap button to instantly reverse the conversion direction, or tap one of the popular conversion shortcuts like km/h to mph, m/s to km/h, or knots to km/h.

• Type the speed value you want to convert
• Select the unit you're converting from (metric, imperial, or nautical)
• Select the unit you want to convert to
• Read the converted speed, the unit rate, and the visual conversion diagram

Speed Conversion Formula

Every speed conversion uses meters per second as a common base unit, since m/s is the SI (International System of Units) standard for speed. To convert any value from one unit to another, the calculator first multiplies the input by that unit's m/s factor to get the speed in meters per second, then divides by the target unit's m/s factor to reach the final answer.

• Step 1: Speed in m/s = Input value × (m/s factor of the "From" unit)
• Step 2: Result = Speed in m/s ÷ (m/s factor of the "To" unit)
• Combined formula: Result = Input value × (From unit's m/s factor ÷ To unit's m/s factor)
• Example shortcut: to convert km/h directly to mph, multiply by 0.621371 (since 1 mph = 1.60934 km/h)

Common Speed Conversion Factors

These are the exact m/s-based conversion factors this calculator uses internally. Knowing them is useful for quick mental estimates even when you don't have the calculator open:

• 1 meter per second (m/s) = 1 m/s (the base unit)
• 1 kilometer per hour (km/h) = 0.2777778 m/s
• 1 mile per hour (mph) = 0.44704 m/s
• 1 foot per second (ft/s) = 0.3048 m/s
• 1 knot (kn) = 0.5144444 m/s = 1.852 km/h
• 1 mph ≈ 1.60934 km/h
• 1 knot ≈ 1.15078 mph

Worked Example: Km/h to Mph

Suppose you want to convert a 100 km/h highway speed limit into mph. First, look up the conversion factor: 1 km/h equals 0.2777778 m/s, and 1 mph equals 0.44704 m/s. Converting via meters per second, 100 km/h × 0.2777778 = 27.77778 m/s, then 27.77778 m/s ÷ 0.44704 = 62.14 mph. So 100 km/h equals about 62.1 mph — exactly what the diagram above shows when you enter 100 in the "From: Kilometer per Hour" field and select "To: Mile per Hour".

Now try a nautical example in the reverse direction: converting 20 knots of wind speed into km/h. Since 1 knot equals 0.5144444 m/s, you multiply first: 20 kn × 0.5144444 = 10.28889 m/s, then convert to km/h by dividing by km/h's factor: 10.28889 ÷ 0.2777778 = 37.04 km/h. This two-step "convert to the base unit, then convert out" method is exactly what powers every conversion this calculator performs, no matter which two speed units you choose.

Metric, Imperial, and Nautical Speed Units

The metric system (meters per second, kilometers per hour) is used by nearly every country in the world for road speed limits, weather reports, and scientific work. The imperial/US system (miles per hour, feet per second) is still standard for road speeds in the United States and the United Kingdom, and feet per second appears frequently in physics and ballistics.

Knots are the standard unit for speed in aviation and maritime navigation worldwide, based on nautical miles per hour, and are used regardless of a country's normal metric or imperial preference. Because these systems don't share a simple round-number relationship, converting between them — such as km/h to mph, knots to km/h, or m/s to mph — normally requires a calculator or a memorized conversion factor, which this tool removes entirely.

Where Speed Conversion Is Used

Speed conversion comes up constantly outside the classroom, in situations where velocity measurements from different systems need to be compared or combined:

• Driving and road travel, converting speed limits and speedometer readings between km/h and mph across borders
• Aviation and maritime navigation, working with knots for airspeed, groundspeed, and wind speed
• Sports science, tracking running pace, cycling speed, or ball/pitch velocity
• Meteorology, reporting wind speed and storm intensity in consistent units
• Physics and engineering, standardizing velocity measurements to m/s for calculations
• Automotive engineering, converting test track and performance data between unit systems