Kilogram

What is a Kilogram?

A kilogram is a way to measure how heavy something is. It is the main unit of mass in the International System of Units, which is the way most of the world measures things. The symbol for kilogram is kg. We often shorten this to "kilo", like when we say "kilos" at the grocery store.

Where Did the Kilogram Come From?

The word "kilogram" comes from old France. It started in 1795, a time when people were making new rules for measuring things. Back then, one kilogram was the weight of one litre of water. Imagine a big bottle of water — that’s about one kilogram!

How is the Kilogram Defined Today?

For many years, there was a special piece of metal called the International Prototype of the Kilogram that people used to decide what one kilogram was. But tiny bits of dirt or wear could change its weight little by little.

Now, scientists use special numbers from nature to define the kilogram. This makes it the same everywhere and forever. One of these numbers is called the Planck constant. This way, anyone with the right tools can measure a kilogram very accurately.

Why Do We Use Kilograms?

We use kilograms to measure many things — from food packages to our own body weight. It helps everyone know just how heavy something is, no matter where they are in the world. Next time you step on a scale or buy groceries, remember you’re using kilograms!