Area converter
Converts areas: m², km², hectares, acres, ft², mi², and NM².
1 ac is 43,560 ft².
- Input
Provenance
- Computed by
- units.area.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 area that crosses systems: a parcel in acres against a plan in hectares, a footprint in square feet against square metres, a survey block in square nautical miles. Both acres are here and kept apart, which matters for land records: the international acre and the US survey acre differ by four parts per million, about 16 square centimetres on an acre and a square metre on a section.
Limitations: An area converts exactly; a measured area does not become more accurate for being converted. The US survey foot and its acre were withdrawn for new work at the end of 2022 and are kept for reading existing records, which is why a value using them is flagged. A square nautical mile is the square of the international nautical mile and is not an official unit of anything -- it appears because airspace and search areas are quoted in it. Nothing here computes the area of a shape; that is the geometry tools.
Worked example: One acre in square feet. 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
- ft2
- Value
- 1 ac
You get
- Converted
- 43,560 ft²
- Input
- 1 ac
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: 75 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.