Pounds to Grams Converter — exact lb to g conversion

Every number this page produces comes from a single defined quantity: one international avoirdupois pound is 453.59237 grams. That is not a measurement with an error bar. In 1959 the national standards laboratories of the United States, United Kingdom, Canada, Australia, New Zealand and South Africa signed the International Yard and Pound Agreement, which defined the pound as exactly 0.45359237 kilograms. Before it, the US and imperial pounds differed in the seventh decimal place and precision engineering had to say which one it meant.

Because the kilogram itself has been fixed by the Planck constant since the 2019 SI redefinition, the chain from pound to gram is now exact end to end. The conversion is therefore a multiplication, and the only question is how many digits to show:

grams = pounds × 453.59237
pounds = grams ÷ 453.59237

The other units follow by definition rather than by a second lookup, which is what keeps them consistent. The avoirdupois ounce is a sixteenth of a pound, so 1 oz = 453.59237 ÷ 16 = 28.349523125 g. The stone is 14 pounds (6,350.29318 g). The US short ton is 2,000 pounds (907,184.74g). Milligrams, grams, kilograms and tonnes are decimal multiples of each other. NIST publishes all of these in Handbook 44, Appendix C, and they are reproduced in the “Every unit” table inside the converter.

Two details decide whether a converter of this kind is trustworthy. The first is rounding order. The tool keeps the full double-precision value internally and rounds only when printing, so chaining conversions never compounds an error. The pounds-and-ounces readout rounds the ounces beforecarrying: 0.9999 lb is 15.9984 oz, which rounds to 16.00 oz, and printing “0 lb 16 oz” would be wrong because sixteen ounces is a pound. Rounding first and carrying second gives the correct “1 lb 0 oz”.

The second is verification. Multiplying by 453.59237 and multiplying by 16 × 28.349523125are the same operation algebraically, but they are not the same sequence of floating-point steps. The converter runs both, plus a third route through NIST's published reciprocal 1 kg = 2.20462262185 lb, and reports whether they agree to within one part in 10¹². If they ever disagree, the panel says so instead of quietly showing one of them.

A word on which pound. This converter handles the avoirdupois pound — groceries, body weight, parcels, gym plates. Precious metals use the troy pound (373.2417216 g) and old pharmacy texts use the apothecaries' pound of the same size but different subdivisions. Those are listed below so a mismatched factor does not slip through unnoticed.

Every gram figure below is 453.59237 × the pound value, computed at full precision and rounded to two decimals for display.

Source: NIST Handbook 44 Appendix C. Need a value that is not listed? Type it into the converter at the top of the page.

Three other units share the name. Using the wrong one is the most common way a weight conversion goes wrong by more than a rounding error.

• NIST Handbook 44, Appendix C — General Tables of Units of Measurement
• US Federal Register, 1 July 1959 — Refinement of Values for the Yard and the Pound (Doc. 59-5442)
• NIST Special Publication 811 — Guide for the Use of the International System of Units, Appendix B.9
• BIPM — The International System of Units (SI Brochure, 9th edition)

These factors were last re-read against the sources above on 2026-08-13. They are definitional constants: they would change only if the CGPM redefined the kilogram or a signatory withdrew from the 1959 agreement, neither of which has happened since it was signed.