kilogram

noun

ki·​lo·​gram ˈki-lə-ˌgram  ˈkē-lə- 

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

The humanoid stands about 5 feet 9 inches tall, weighs roughly 175–180 pounds (79–82 kilograms), and is intended for tasks such as reconnaissance, bomb disposal, and other high-risk ground operations. —Jijo Malayil, Interesting Engineering, 16 Mar. 2026

The humpback whale is possibly the most accomplished vocalist in the ocean, and those songs come from a giant animal that can weigh more than 55,000 pounds (24,947 kilograms). —ABC News, 16 Mar. 2026

Placer County Sheriff's Office During the operation, investigators reported seizing 65 pounds of methamphetamine, more than 7 kilograms of cocaine, about half a pound of MDMA, 26 guns, more than $100,000 in cash and what authorities described as a DMT laboratory. —Richard Ramos, CBS News, 16 Mar. 2026

Before last summer’s war, the International Atomic Energy Agency estimated that Tehran possessed more than 400 kilograms enriched to 60 percent—dangerously close to weapons-grade and sufficient for roughly 11 nuclear weapons if further enriched. —Richard Goldberg, The Atlantic, 16 Mar. 2026

Word History

Etymology

French kilogramme, from kilo- + gramme gram

First Known Use

1797, in the meaning defined at sense 1

Phrases Containing kilogram

• kilogram-meter
• meter-kilogram-second

Rhymes for kilogram

• abraham
• anagram
• cablegram
• cofferdam
• dendrogram
• diagram
• diaphragm
• epigram
• hexagram
• histogram
• hologram
• instagram

Kids Definition

kilogram

noun

ki·​lo·​gram ˈkē-lə-ˌgram  ˈkil-ə- 

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

variants or chiefly British kilogramme

ˈkil-ə-ˌgram  ˈkē-lə- 

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