Weight and Mass Converter

Use this calculator to convert between common units of weight and mass.

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From Kilogram Gram Milligram Ton Pound Ounce Carat Atomic Mass Unit Grain Stone [UK]

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To Kilogram Gram Milligram Ton Pound Ounce Carat Atomic Mass Unit Grain Stone [UK]

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Why So Many Units of Weight?

Historically, weight was measured using containers filled with plant seeds. The "carat," still used for gems, is derived from the carob seed. Ancient civilizations like the Babylonians and Romans developed their own systems based on local standards, such as the weight of a coin or a volume of water.

The British Imperial System (which influenced the US system) evolved over centuries, with units like the pound and ounce. In contrast, the metric system (kilogram, gram) was developed by scientists in 18th-century France to be a logical, decimal-based system, making conversions far simpler. Today, while the metric system is the global standard for science and most countries, traditional units remain in common use in places like the United States.