Convert lbs to kg

Pound

Definition: A pound (symbol: lb) is a unit of mass used in the imperial and US customary systems of measurement. Since 1959, the international avoirdupois pound has been officially defined as exactly 0.45359237 kilograms.

History/origin: The pound originated from the Roman libra (hence the "lb" abbreviation), which was equivalent to 328.9 grams. Various definitions of the pound were used throughout Europe in the Middle Ages, differing from city to city and country to country.

The avoirdupois pound, which is the most commonly used pound today, was established in England during the 13th century and was used for weighing wool. The avoirdupois system introduced the concept of a 16-ounce pound, which eventually became the standard for most commodities.

Prior to the international agreement in 1959 that standardized the pound to exactly 0.45359237 kilograms, the pound was defined differently in various countries. The United States and countries of the Commonwealth of Nations agreed to this definition to ensure international consistency in trade and commerce.

Current use: The pound is primarily used in the United States and, to a varying extent, in other countries historically tied to the British Empire, such as the United Kingdom, where it remains in common use despite official adoption of the metric system. It's commonly used for personal weight, food measurements, and various commercial applications.

Kilogram

Definition: A kilogram (symbol: kg) is the base unit of mass in the International System of Units (SI). It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10⁻³⁴ when expressed in the unit J⋅s, which is equal to kg⋅m²⋅s⁻¹.

History/origin: The kilogram was originally defined in 1795 as the mass of one liter (cubic decimeter) of water. In 1799, a platinum artifact was fabricated to represent the kilogram. This artifact, known as the International Prototype of the Kilogram (IPK), was stored at the International Bureau of Weights and Measures (BIPM) in Sèvres, France.

For nearly 130 years, the kilogram was defined as exactly the mass of the IPK. However, in 2019, the kilogram was redefined in terms of the Planck constant, making it based on invariant constants of nature rather than a physical artifact that could change over time due to contamination or wear.

Current use: The kilogram is used globally as the standard unit of mass in science, commerce, and everyday life in most countries that have adopted the metric system. It's used for measuring the mass of objects ranging from groceries to industrial materials to scientific specimens.