Pound

The US everyday mass unit.

Mass

How it's defined

Since 1959, defined as exactly 0.45359237 kilograms. Like the inch, it is officially a metric unit in disguise.

1 lb = 0.45359237 kg — exact since 19591 lb = 16 oz — exact

Convert — honestly

lb equals

0.45359237 kg

Kilogram · factor exact — the base unit itself

453.59237 g

Gram · factor exact — exact by definition

0.00045359237 t

Tonne · factor exact — exact by definition

2.7316e+26 u

Atomic mass unit · factor measured — measured (CODATA), carries uncertainty

Conversions run through the kilogram using the stated factors — no rounding beyond display precision, and every factor says whether it's exact or measured.

Where you meet it

US body weights, produce aisles, and package labels
The "psi" pressure unit carries it

Other ways to measure mass

kg Kilogram g Gram t Tonne u Atomic mass unit

Source

This page is an authored summary of the authoritative definition — checkable one click away.

NIST Special Publication 811 — Guide for the Use of the SI