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.
The company calculates savings per kilogram of recycled cotton, and a product’s contribution to overall savings depends on how much is used. — Alexandra Harrell, Footwear News, 9 Oct. 2026 Eel smuggling The panel also looked at the smuggling of baby eels, one of the most lucrative natural resources in Haiti, with one kilogram going for between $3,000 and $5,000 on the international market. — Jacqueline Charles, Miami Herald, 7 Oct. 2026 Electricity generated at wind and solar power plants is now widely available, but the cost of hydrogen generated this way is around $5 per kilogram. — Ameya Paleja, Interesting Engineering, 5 Oct. 2026 On land, our CENTAURI platforms deliver multi-gigabit wireless laser backhaul in compact, 3-kilogram devices that deploy in minutes without RF spectrum licensing. — Rohit Jha, Forbes.com, 1 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

Browse Nearby Words

Cite this Entry

“Kilogram.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/kilogram. Accessed 14 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

More from Merriam-Webster on kilogram

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!