Kilograms explained

The kilogram is the base unit of mass in the International System of Units (SI). One kilogram approximately represents the mass of one liter of water at its maximum density, which occurs at a temperature of about 4°C. This relationship is not coincidental but historical. Its precise definition relies on fundamental constants of nature, ensuring unparalleled accuracy and stability in mass measurement. The kilogram is unique among SI units as it includes a prefix ("kilo-") in its name, signifying 1,000 grams.

Symbol

The symbol for the kilogram is kg.

Standardized Unit System

The kilogram is part of the International System of Units (SI) and serves as the base unit for mass. Below is a table of some related units within the SI system:

Unit Symbol Description
Metric Ton t 1,000 kilograms
Kilogram (Base Unit) kg The base unit of mass in SI
Gram g 1/1,000 of a kilogram
Milligram mg 1/1,000,000 of a kilogram

It's important to note that while these units are primarily used for mass, they are often used interchangeably with weight in everyday contexts on Earth, where the acceleration due to gravity is relatively constant. However, strictly speaking, weight is a force and would be measured in newtons (N) in the SI system

Tools to Measure Kilograms

Mass in kilograms can be measured with various instruments:

  • Kibble Balance: A highly precise instrument used in metrology laboratories.
  • Weighing Scales: Commonly used in households, industries, and scientific research.
  • Digital Balances: Provide accurate readings for laboratory and commercial use.

Origin of the Kilogram

The kilogram originated during the French Revolution in 1795 as the mass of one liter of water at its maximum density. In 1799, it was formalized using a platinum artifact called the "Kilogramme des Archives." Later, in 1889, the International Prototype Kilogram (IPK), made from platinum-iridium, became the global standard. In 2019, the kilogram was redefined based on Planck's constant to ensure greater precision and universality.

FAQs About the Kilogram

1. Why was the kilogram redefined?

The kilogram was redefined in 2019 to base it on fundamental constants like Planck’s constant instead of a physical object. This ensures long-term stability and precision.

2. How does a Kibble balance work?

A Kibble balance measures mass by balancing gravitational force with an electromagnetic force generated by an electric current. It replaces reliance on physical objects like the IPK.

3. What is the difference between mass and weight?

Mass (measured in kilograms) refers to the amount of matter in an object, while weight (measured in newtons) is the force exerted by gravity on that object.

Convert kilograms to other weight and mass units

In this section, you find an overview of all conversions from kilograms to other weight and mass units available on this website.