What is being measured?
Mass is distinct from force or weight. Pounds of mass and pounds-force belong to different quantities.
Pounds and ounces use international avoirdupois mass. US tons are short tons; a metric carat is 200 mg.
Meaning of lb
Pounds uses the symbol lb in this library and measures mass. Under the stated reference convention, 1 lb = approximately 0.45359237 kg. This equivalence changes how a known value is written. It does not increase measurement accuracy or establish whether a measurement is appropriate to a real application.
Conversion method
Multiply the value by the source factor (0.45359237), then divide by the target factor (1). The factor ratio expresses the same mass measurement in the other unit.
Worked example
For a known value of 10 lb, the reference conversion gives 4.5359237 kg. Converting that result back gives approximately 10 lb. This reverse check helps catch a reversed factor, but matching round-trip arithmetic alone does not independently verify a source definition.
Common reference values
| Input (lb) | Reference equivalent (kg) |
|---|---|
| 1 | 0.45359237 |
| 5 | 2.26796185 |
| 10 | 4.5359237 |
| 25 | 11.33980925 |
| 50 | 22.6796185 |
| 100 | 45.359237 |
Compare one lb with other units
| Target unit | Equivalent of 1 lb | Definition guide |
|---|---|---|
| Kilograms (kg) | 0.45359237 | Read definition |
| Grams (g) | 453.59237 | Read definition |
| Ounces (oz) | 16 | Read definition |
| milligrams (mg) | 453592.37 | Read definition |
| metric tons (t) | 0.00045359237 | Read definition |
| US short tons (US ton) | 0.0005 | Read definition |
| stones (st) | 0.0714285714286 | Read definition |
| carats (ct) | 2267.96185 | Read definition |
Precision and common mistakes
- Keep the source and target quantity consistent. A matching symbol is not enough to establish a compatible definition.
- Record the original measurement precision. Showing twelve significant digits in a table does not make a rounded input more precise.
- Check symbol capitalization, prefixes and any regional convention in the source. Use the displayed unit definition rather than a similarly named unit.
- Factors involving repeating fractions or π use finite numerical precision. Round the final answer to the precision justified by your input.
Use a working converter
- Mass converter
- Pounds to milligrams converter
- Pounds to Kilograms converter
- Pounds to Ounces converter
- Pounds to stones converter
- Pounds to US short tons converter
Source and verification scope
Examples and tables are computed from the versioned unit definitions used by the linked converters. The source access dates appear below. Computandum is independent of the cited organizations; a citation does not mean that a publisher endorses this page or an actual project.
Sources
- NIST / BIPM: NIST: unit conversion factors ↗ · 2026-10-08