About

Land area misstatement in property transactions causes measurable financial loss. A parcel listed as 40 acres is exactly 16.187 ha, not the rounded 16.2 ha that appears in casual estimates. That 0.013 ha difference represents 130 m² of land. This converter applies the exact factor k = 0.40468564224 derived from the international foot definition (1 ft = 0.3048 m exactly) and the statutory acre (43,560 ft²). Results carry full floating-point precision before display rounding.

Note: this tool assumes the international acre. The US survey acre, deprecated by NIST since 2023, differs by approximately 2 parts per million. For parcels under 10,000 acres, the difference is below 0.02 ha and negligible for most legal descriptions.

Formulas

The conversion between acres and hectares is a linear scaling by the exact constant k:

A_ha = A_ac × 0.40468564224

The inverse conversion uses the reciprocal:

A_ac = A_ha × 2.47105381467

This constant derives from the chain of exact definitions:

1 acre = 43,560 ft² = 43,560 × 0.3048² m² = 4,046.8564224 m²

k = 4,046.856422410,000 = 0.40468564224

Where A_ha is the area in hectares, A_ac is the area in acres, k is the exact conversion factor, 0.3048 is the international foot in meters (exact), and 10,000 m² = 1 ha by definition.

Reference Data

Acres	Hectares	Square Meters	Common Reference
0.25	0.1012	1,011.71	Typical suburban lot (US)
0.5	0.2023	2,023.43	Large residential lot
1	0.4047	4,046.86	Standard acre reference
2.471	1.0000	10,000.00	One hectare equivalent
5	2.0234	20,234.28	Small farm / orchard
10	4.0469	40,468.56	Market garden
40	16.1874	161,874.26	Quarter section (US survey)
100	40.4686	404,685.64	Mid-size ranch
160	64.7497	647,497.03	Homestead Act parcel
247.105	100.0000	1,000,000.00	One square kilometer
320	129.4994	1,294,994.05	Half section
500	202.3428	2,023,428.21	Large agricultural holding
640	258.9988	2,589,988.11	One section (1 sq mile)
1,000	404.6856	4,046,856.42	Large estate
2,500	1,011.7141	10,117,141.06	Timber tract
5,000	2,023.4282	20,234,282.11	Large ranch
10,000	4,046.8564	40,468,564.22	~40 km² wilderness area
23,040	9,324.0083	93,240,083.88	One township (36 sections)

Frequently Asked Questions

Most converters round to 2-4 decimal places, which introduces compounding error for large parcels. A 640-acre section rounded to 259.00 ha instead of the exact 258.9988 ha misrepresents roughly 1,200 m² of land. This tool preserves full floating-point precision internally and displays up to 6 significant digits by default.

The international acre uses the international foot (0.3048 m exactly). The US survey acre used the older survey foot (1200/3937 m), making it approximately 4,046.8726 m² vs 4,046.8564 m². The difference is about 2 parts per million. NIST officially deprecated the US survey foot on January 1, 2023 (Federal Register 85 FR 33530), so all new work should use the international definition that this tool implements.

It does not. Both the acre and the hectare are abstract area units defined by length standards (the meter and the foot). They do not depend on local gravitational field, temperature, or altitude. Unlike mass-weight conversions, area-to-area conversions are purely geometric ratios and remain constant regardless of physical conditions.

The conversion factor used here (0.40468564224) is the exact value recognized by ISO 80000-3 and NIST. However, legal land descriptions in many jurisdictions carry specific rounding conventions. For example, Australian Torrens titles typically round hectares to 3 decimal places. Always verify the rounding convention required by your local land registry before transcribing values from any converter.

The hectare is accepted for use with SI but is not a coherent SI unit. The SI system uses the square meter (m²) as its area unit. The hectare persists because expressing agricultural and forestry areas in raw m² produces unwieldy numbers. The CGPM (General Conference on Weights and Measures) has repeatedly declined to deprecate it due to widespread practical use, particularly in land administration across Europe, South America, and Australia.

JavaScript uses IEEE 754 double-precision floats with approximately 15-17 significant decimal digits. For areas up to 10¹² acres (far exceeding the Earth's land surface of roughly 36.5 billion acres), the conversion remains accurate to better than 1 mm². Precision is not a practical concern for any real-world land measurement scenario.