Convert a speed into miles per hour, kilometers per hour, meters per second, knots, and feet per second in one quick step.
Table of contents
How to use our Speed Conversion Converter
- Enter the number in Speed value.
- Choose the original unit in Convert from, such as miles per hour or knots.
- Pick Decimal places if you want more or less rounding in the results.
- Click Calculate to see the common conversions and check Entered speed to make sure you converted the unit you meant to use.
Definitions
Speed: How fast something moves.
Miles per hour (mph): A road-speed unit commonly used in the United States.
Kilometers per hour (km/h): A road-speed unit commonly used in many countries outside the US.
Meters per second (m/s): A standard science unit for speed.
Knots (kn): A speed unit based on nautical miles per hour, often used at sea and in aviation [1].
Feet per second (ft/s): A speed unit that tells how many feet are traveled each second.
Decimal places: How many digits appear after the decimal point in each converted result.
Common mistakes and quick fixes
Mistake: Typing text like "60 mph" into Speed value instead of just the number.
Fix: Enter only the numeric part in Speed value , then choose the unit in Convert from .
Mistake: Leaving Convert from on the wrong unit, such as mph when your number is really km/h.
Fix: Match Convert from to the unit you started with before you calculate.
Mistake: Thinking Knots means the same thing as miles per hour.
Fix: Read the Knots result separately; knots are a different speed unit used for boating and aviation.
Mistake: Rounding too much and thinking a tiny result is exactly zero.
Fix: Increase Decimal places if Meters per second , Knots , or another result looks too rounded.
Mistake: Forgetting what you entered after changing settings.
Fix: Check Entered speed to confirm the original number and unit are the ones you wanted.
Limitations & Key Assumptions / Boundary Conditions
- This tool converts only the five listed units: mph, km/h, m/s, kn, and ft/s.
- It treats the entered value as a speed only. If direction matters, that is velocity, which is not shown here.
- Negative values are allowed for math and physics use, but real-world speed is usually zero or greater.
- Displayed results are rounded to the selected Decimal places, so copied values may hide tiny differences.
- Very small converted values can appear as 0 when rounding is strong; increase Decimal places for more detail.
- This page does not include Mach, pace, or Beaufort because those need extra assumptions or different rules.
Methodology
How the converter works
The calculator first changes your input into meters per second, then changes that base value into each result unit. Using one base unit keeps every result consistent with the others.
speed_mps = input_value * factor_to_mps[from_unit]
target_value = speed_mps / factor_to_mps[target_unit]
Conversion factors used
1 mph = 0.44704 m/s
1 km/h = 0.2777777778 m/s
1 m/s = 1 m/s
1 kn = 0.5144444444 m/s
1 ft/s = 0.3048 m/s
Mini example
If you enter 60 for Speed value and choose Convert from = mph, the base step is 60 x 0.44704 = 26.8224 m/s. Then the tool converts that same base value into the other units, such as 26.8224 / 0.2777777778 = 96.56064 km/h.
How to read the results
Miles per hour is most useful for US driving, Kilometers per hour for many other road systems, Meters per second for science work, Knots for boating and aviation [2], and Feet per second for some physics and engineering problems.
Assumptions and limits
The math assumes standard fixed unit definitions and then rounds the final display to your chosen Decimal places. If a result looks like 0 for a tiny value, the actual unrounded value may be nonzero.