kilogram

American  

[kil-uh-gram] / ˈkɪl əˌgræm /

especially British, kilogramme

noun

1. a unit of mass equal to 1,000 grams: the basic unit of mass in the International System of Units (SI). Up until 2019 the kilogram was defined as equal to the mass of an international prototype, a platinum-iridium cylinder kept in Sèvres, France. The kilogram has since been redefined in terms of universal physical constants, including the speed of light and Planck's constant. kg

2. a unit of force and weight, equal to the force that produces an acceleration of 9.80665 meters per second per second when acting on a mass of one kilogram. kg

---

kilogram British  

/ ˈkɪləʊˌɡræm /

noun

1. one thousand grams

2. the basic SI unit of mass, equal to the mass of the international prototype held by the Bureau International des Poids et Mesures. One kilogram is equivalent to 2.204 62 pounds

---

kilogram Scientific  

/ kĭl′ə-grăm′ /

1. The basic unit of mass in the metric system, equal to 1,000 grams (2.2 pounds).

2. See Table at measurement

---

kilogram Cultural  

1. A unit of mass in the metric system, equal to one thousand grams. The weight of a one-kilogram mass is slightly over two pounds.

---

Etymology

Origin of kilogram

From the French word kilogramme, dating back to 1790–1800. See kilo-, -gram ²

Explanation

A kilogram is a unit of measurement that's a bit more than two pounds. The liter bottle of soda in your refrigerator weighed about one kilogram when it was full. The United States is one of only three countries that has not adopted the metric system as its official system of measurement. In the United States, then, the pound is the basic unit used to measure mass, while most countries use the kilogram. So your bulldog weighs in at 100 pounds at your home in Florida but 45.36 kilograms when you move to Ireland. Originally, a kilogram was defined as the mass of a liter of water.

Example Sentences

Montgomery said EPA officials would proactively reach out to property owners whose lots had lead levels above the federal benchmark of 200 milligrams per kilogram.

From Los Angeles Times • May 21, 2026

SpaceX’s workhorse launch vehicle can carry 22,500 kg to orbit at $3,289 a kilogram.

From MarketWatch • May 21, 2026

Prices were closer to $50 per kilogram for years.

From Barron's • May 18, 2026

According to the researchers, it stores more than 1.6 megajoules of energy per kilogram.

From Science Daily • May 15, 2026

Turns out, through a neat set of chemical reactions with the Martian atmosphere, for every kilogram of hydrogen you bring to Mars, you can make thirteen kilograms of fuel.

From "The Martian" by Andy Weir