Pound (lb)

Definition

Exactly 0.45359237 kilograms — the international avoirdupois pound fixed by the 1959 agreement of the US, UK and Commonwealth.

History

The pound descends from the Roman libra, whose name still gives the symbol lb. Many regional pounds circulated for centuries before the 16-ounce avoirdupois pound became the English-speaking standard for trade. In 1959 the United States, the United Kingdom and other Commonwealth countries signed the international yard and pound agreement, fixing the pound at exactly 0.45359237 kilograms.

Where it is used

The pound is the everyday unit of weight in the United States, and informally in the United Kingdom, for body weight, food packaging and shipping, while most of the world states the same weights in kilograms.

Typical uses include body weight in the US, gym plates, shipping weights.

Conversion pages

These pages convert pound to or from another unit in weight.

• Kilogram to pound
• Stone to pound

Other Weight units

• Kilogram (kg)
• Gram (g)
• Ounce (oz)
• Stone (st)
• Milligram (mg)
• Microgram (mcg)
• Tonne (t)

Sources

• NIST HB 44 NIST Handbook 44, Appendix C §5 (Tables of Equivalents) · Dataset reviewed Nov 11, 2026