Mass converter
Converts masses: kg, g, lb, oz, and metric tonnes.
2,550 lb is 1,156.6605 kg.
- Input
Provenance
- Computed by
- units.mass.convert 1.0.0, core 0.1.0
- Model
- Exact unit definitions
- Accuracy
- Exact to double precision: each conversion is one correctly rounded ratio of exact definitions
- Notes
- None
- Cites
- National Institute of Standards and Technology, Guide for the Use of the International System of Units (SI), NIST Special Publication 811; National Institute of Standards and Technology, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices, NIST Handbook 44
Something look off?
How we got thisFormula, worked example, sources, and proof
Model: Exact unit definitions
Accuracy: Exact to double precision: each conversion is one correctly rounded ratio of exact definitions
When to use this: Use this for any weight that has to move between systems: an aircraft or vehicle weight in pounds against a limit in kilograms, a payload in ounces, a load in tonnes. Weight and balance, freight manifests and equipment lists are quoted in whichever system the document came from, and the limit is usually in the other one.
Limitations: These are masses, not forces. A pound here is the international avoirdupois pound of mass, not the pound-force, and the two are the same number only where gravity is standard -- which is why the pressure converter builds psi from this pound times standard gravity rather than treating them as interchangeable. The tonne is the metric tonne of 1,000 kg, not the short ton of 2,000 lb nor the long ton of 2,240 lb, neither of which is offered, so a document saying only ton has to be read before it is converted.
Worked example: 2,550 lb in kilograms. Source: Exact unit definitions (NIST SP 811 Appendix B). It is golden test vector v001, and every build checks the tool still gives its answer within its tolerance.
You enter
- To unit
- kg
- Value
- 2550 lb
You get
- Converted
- 1,156.6605 kg
- Input
- 2,550 lb
Review: Not yet independently reviewed by a metrologist.
Last verified: 2026-09-18, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.
Status: version 1.0.0, core 0.1.0. See this tool in the verification report.
Checked against: 24 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.
Sources
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, National Institute of Standards and Technology, 2008 edition. Appendix B.8, Factors for units listed alphabetically.
- Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices, NIST Handbook 44, National Institute of Standards and Technology, 2026 edition. Appendix C, General Tables of Units of Measurement.