Pound (lb)

US & ImperialCurrent unit

Exactly 0.45359237 kg, divided into 16 ounces. The standard unit of weight in the US and common in the UK.

1 pound = 0.45359237 kilograms (exactly).

About the pound

Why is pound abbreviated lb? The answer is Roman. The English word comes from the Latin libra pondo, roughly the weight measured in libra, and the symbol keeps the first word. The Roman libra was divided into 12 unciae. The avoirdupois pound of 16 ounces came into general use around 1300 and was initially equal to 6,992 troy grains; under Elizabeth I it was redefined as 7,000 grains. The UK's Weights and Measures Act 1878 set the imperial standard pound as a platinum cylinder, and the troy pound was abolished for trade the following year.

Today the pound is defined from the kilogram. The International Yard and Pound Agreement of 1959 fixed it at exactly 0.45359237 kg, and the UK's Weights and Measures Act 1963 wrote the same figure into law. Pounds remain the everyday unit for body weight, groceries and shipping in the United States and are widely used in the UK. The word also survives in odd places: a six-pounder cannon was named for the weight of its shot, not its own.

Sources: Wikipedia: Pound (mass); NIST Guide to the SI, Appendix B.8 (mass conversions)

Pound conversion chart

1 pound expressed in every other weight & mass unit:

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