Pounds to kilograms converter

Pounds are often used on parcel labels and equipment specifications. This is avoirdupois mass, rather than a force rating. If the source gives pounds plus ounces, combine them correctly before conversion. A carrier's billed weight can also depend on package dimensions.

One pound is exactly 0.45359237 kilograms. The international avoirdupois pound is defined as exactly 0.45359237 kg (1959 agreement).

Multiply the number of pounds by 0.45359237. For example, 150 lb × 0.45359237 = 68.038856 kg. To go the other way, divide by 0.45359237.

Multiply by 0.45. That is 0.8% low of the exact factor 0.45359237, so 150 lb comes out as 67.5 kg instead of 68.0389.

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 3 worked examples whose answers come from independent sources; for example, “150 lb to kg” is checked against Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions).

NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B; NIST Handbook 44, Appendix C: General tables of units of measurement; BIPM, The International System of Units (SI Brochure), 9th edition.