1
: the base unit of mass in the International System of Units that is defined by setting the fixed numerical value of Planck's constant to 6.62607015 x 10–34 joule seconds see Metric System Table
2
: a unit of force or weight equal to the weight of a kilogram mass under a gravitational attraction equal to that of the earth

Did you know?

The original concept of the kilogram, as the mass of a cubic decimeter of water (a bit more than a quart), was adopted as the base unit of mass by the new revolutionary government of France in 1793. In 1875, in the Treaty of the Meter, 17 countries, including the U.S., adopted the French kilogram as an international standard. In 1889 a new international standard for the kilogram, a metal bar made of platinum iridium, was agreed to; President Benjamin Harrison officially received the 1-kilogram cylinder for the U.S. in 1890. But no one uses that bar very often; for all practical purposes, a kilogram equals 2.2 pounds.

Examples of kilogram in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Its lift capability to low-Earth orbit is nearly 29,000 pounds (13,000 kilograms). — Stephen Clark, ArsTechnica, 15 Oct. 2026 As Falcon 9's booster began the journey to its landing zone, the rocket's second stage continued onward to orbit with Dragon and the capsule's 6,300 pounds (2,860 kilograms) of cargo for the ISS. — Josh Dinner, Space.com, 13 Oct. 2026 The suspect allegedly organized and carried out the detonation of at least four bombs between 14 and 27 kilograms (around 31 to 62 pounds) at a depth of 70 to 80 meters (230 feet to 263 feet) near the Danish island of Bornholm. — ABC News, 13 Oct. 2026 According to Colombian police accounts cited by El Tiempo, Pulido coordinated the shipment of approximately two tons of cocaine and 17 kilograms of heroin to Europe in 1999. — Antonio María Delgado, Miami Herald, 12 Oct. 2026 See All Example Sentences for kilogram

Word History

Etymology

French kilogramme, from kilo- + gramme gram

First Known Use

1797, in the meaning defined at sense 1

Time Traveler
The first known use of kilogram was in 1797

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Cite this Entry

“Kilogram.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/kilogram. Accessed 20 Oct. 2026.

Kids Definition

1
: the basic unit of mass in the metric system that has been accepted by international agreement and is nearly equal to the mass of 1000 cubic centimeters of water at its highest density see metric system
2
: the weight of a kilogram mass on the earth
he weighs 80 kilograms
see metric system

Medical Definition

kilogram

noun
ki·​lo·​gram
1
: the base unit of mass in the International System of Units that is equal to the mass of a prototype agreed upon by international convention and that is nearly equal to the mass of 1000 cubic centimeters of water at the temperature of its maximum density
2
: a unit of force equal to the weight of a kilogram mass under a gravitational attraction equal to that of the earth

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