21 pounds in kilograms

Conversion

21 pounds is equivalent to 9.52543977 kilograms.^[1]

Conversion formula
How to convert 21 pounds to kilograms?

We know (by definition) that: $1 lb \approx 0.45359237 kg$

We can set up a proportion to solve for the number of kilograms.

\frac{1 lb}{21 lb} \approx \frac{0.45359237 kg}{x kg}

Now, we cross multiply to solve for our unknown $x$ :

x kg \approx \frac{21 lb}{1 lb} * 0.45359237 kg \to x kg \approx 9.52543977 kg

Conclusion: $21 lb \approx 9.52543977 kg$

21 pounds is equivalent to 9.52543977 kilograms

Conversion in the opposite direction

The inverse of the conversion factor is that 1 kilogram is equal to 0.104982029611846 times 21 pounds.

It can also be expressed as: 21 pounds is equal to $\frac{1}{0.104982029611846}$ kilograms.

Approximation

An approximate numerical result would be: twenty-one pounds is about nine point five two kilograms, or alternatively, a kilogram is about zero point one zero times twenty-one pounds.

Units involved

This is how the units in this conversion are defined:

Pounds

The pound or pound-mass (abbreviations: lb, lbm for most pounds) is a unit of mass used in the imperial units, United States customary and other systems of measurement. A number of different definitions have been used, the most common today being the international avoirdupois pound which is legally defined as exactly 0.45359237 kilograms, and which is divided into 16 avoirdupois ounces.[3] The international standard symbol for the avoirdupois pound is lb.The unit is descended from the Roman libra (hence the abbreviation lb). The English word pound is cognate with, among others, German Pfund, Dutch pond, and Swedish pund. All ultimately derive from a borrowing into Proto-Germanic of the Latin expression lībra pondō a pound by weight, in which the word pondō is the ablative case of the Latin noun pondus.

Wikipedia page of pounds

Kilograms

The kilogram is the base unit of mass in the International System of Units (the Metric system) and is defined as being equal to the mass of the International Prototype of the Kilogram. The avoirdupois (or international) pound, used in both the imperial and US customary systems, is defined as exactly 0.45359237 kg, making one kilogram approximately equal to 2.2046 avoirdupois pounds. Other traditional units of weight and mass around the world are also defined in terms of the kilogram, making the IPK the primary standard for virtually all units of mass on Earth.

Wikipedia page of kilograms

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.

Conversion

Conversion formula How to convert 21 pounds to kilograms?

Conversion in the opposite direction

Approximation

Conversion formula
How to convert 21 pounds to kilograms?