21 feet per second in kilometers per hour

Conversion

21 feet per second is equivalent to 23.04288 kilometers per hour.^[1]

Conversion in the opposite direction

The inverse of the conversion factor is that 1 kilometer per hour is equal to 0.0433973531086392 times 21 feet per second.

It can also be expressed as: 21 feet per second is equal to $\frac{1}{0.0433973531086392}$ kilometers per hour.

Approximation

An approximate numerical result would be: twenty-one feet per second is about twenty-three point zero three kilometers per hour, or alternatively, a kilometer per hour is about zero point zero four times twenty-one feet per second.

Units involved

This is how the units in this conversion are defined:

Feet Per Second

'The foot per second (plural feet per second) is a unit of both speed (scalar) and velocity (vector quantity, which includes direction). It expresses the distance in feet (ft) traveled or displaced, divided by the time in seconds (s, or sec). The corresponding unit in the International System of Units (SI) is the metre per second.Abbreviations include ft/s, ft/sec and fps, and the rarely used scientific notation ft s−1.'

Wikipedia page of feet per second

Kilometers Per Hour

"The kilometer per hour is a unit of speed, expressing the number of kilometres travelled in one hour. The unit symbol is km/h. Worldwide, it is the most commonly used unit of speed on road signs and car speedometers."

Wikipedia page of kilometers per hour

Footnotes

[1] The precision is 15 significant digits (fourteen digits to the right of the decimal point).

Results may contain small errors due to the use of floating point arithmetic.