Bar (unit) facts for kids

The bar, decibar, and millibar are special units used to measure pressure. Think of pressure as how much force is pushing on a certain area. While these units are not part of the main SI (the global system of measurement), they are still very useful. The bar, for example, is often used because it's very close to the normal atmospheric pressure (the air pressure around us).

Understanding Bar Units

Let's look at how these units relate to other ways of measuring pressure:

• 1 bar is equal to 100,000 pascals (Pa). It's also 1,000,000 dynes per square centimeter.
• 1 decibar (dbar) is 0.1 of a bar. This means it's 10,000 pascals.
• 1 millibar (mbar) is 0.001 of a bar. This is equal to 100 pascals.

A pascal is a unit of pressure. It means one newton of force spread over one square meter. A newton is a unit of force.

Where Did the Bar Come From?

The word bar comes from the Greek word βάρος (baros). This word means "weight."

The official symbol for the bar is "bar." An older symbol, "b," is not used anymore. However, you might still see "mb" instead of the correct "mbar" for millibars.

Sir Napier Shaw first defined the bar and millibar in 1909. These units then became used internationally in 1929.

Images for kids

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  This map shows atmospheric pressure in millibars (mbar) or hectopascals (hPa).

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  A tire-pressure gauge showing pressure in bar (outside) and pounds per square inch (inside).

See also

In Spanish: Bar (unidad de presión) para niños