Convert Pounds to Kilograms

In both science related fields, cooking, and for other daily chores, individuals commonly have to figure out how to convert pounds to kilograms. The pound is the unit of measure for mass primarily used in the United States and countries that use the imperial weight system. The type of pound measure used in these countries is called the avoirdupois pound that is defined as 0.45359237 kilograms in size.

History of the Pound Unit of Measure

The pound has been used in various forms throughout the world for a number of applications. In the United Kingdom, the various types of pound measure used over the course of time have included the current avoirdupois, tower, London, and merchant pounds. Other than the use of the Troy pound for use in precious metals (changed from the tower pound in 1528), the avoirdupois pound is the unit of measure primarily used today

The avoirdupois pound was first used around 1300 A.D. and was equal to 6992 troy grains and divided into 16 ounces. The definition was later changed to be 7,000 troy grains and was later defined by the U.K.’s Weights and Measures Act of 1878. By May of 1898, the approximation to the kilogram of the pound was legally stated to be 0.45359243 kg. It would later be refined in 1963 to be a mass equivalent to 0.45359237 kg to be consistent with the international standard defined in 1959.

Similar to the U.K, the pound unit of measure (or livre) has been used since the Middle Ages. In the late 9^th century to the mid 1300’s, the livre esterlin was equivalent to approximately 5,665 grains or 367.1 grams. From this point to the late 1700’s, the livre de Paris was equivalent to 489.5 grams. In 1812, a livre was measured as an equivalent to one metric pound, or 500 grams.

When Did Kilograms Start to Be Used?

The metric standard was created by the Metre Convention that was signed on May 20, 1875 and is also referred to as the SI system. The kilogram is the base unit of mass in the system, and is defined to being equivalent to the IPK (International Prototype Kilogram) that is almost equivalent to the mass of a liter of water. One kilogram in the system is approximately 2.2046 avoirdupois pounds. Although the metric system and kilogram were adopted for commercial use, the standard set of prefixes in powers of ten have made it popular for use in both engineering and scientific circles.

Today, the United States is the only major industrialized country which has not adopted the metric system for the country’s official system of measurement. The use of the kilogram and other SI units has been approved since 1866. In the United Kingdom, the system is approved for use, but not universally adopted either.

Steps to Convert Pounds to Kilograms (Manually)

Step 1 – Multiply the number of pounds by the conversion ratio 0.45359237. If you have something that weighs two pounds (avoirdupois type), it will weigh 0.90 kilograms.

Step 2 – Alternatively, if you prefer to divide vice multiple, the number of everyday pounds can be divided by 2.204622621848776 to get the approximate weight in kilograms.