Kilogram (kg)

Definition

The kilogram (kg) is the base unit of mass in the International System of Units (SI). It is defined as the mass of the International Prototype of the Kilogram, a platinum-iridium cylinder stored in France. As of May 20, 2019, the kilogram is defined using the Planck constant, valued at 6.62607015 × 10⁻³⁴ kg·m²/s.

History

The kilogram was first defined in 1795 as the mass of a liter of water at its maximum density. In 1889, the International Prototype was adopted as the standard. Over time, the reliance on a physical object for definition led to inconsistencies, prompting the 2019 redefinition based on fundamental constants.

Uses

The kilogram is widely used in everyday life, science, and engineering. It is the standard unit for mass in most countries, essential in commerce, health (body weight), and various scientific fields.

Conversions

  • 1 kg = 1000 grams
  • 1 kg = 2.20462 pounds
  • 1 kg = 35.274 ounces

Fun Facts

  • The kilogram was the only SI base unit with a physical object as its standard until 2019.
  • A common misconception is that a kilogram is a measure of weight; it is actually a measure of mass.
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