Acres to Hectares Calculator

How the acres to hectares conversion works

An acre is the US customary unit of land area; a hectare is the metric one, equal to 10,000 square metres. One acre is exactly 0.40468564224 hectares, so the calculator multiplies the acreage you enter by that number and shows the answer in hectares, with square metres and square feet alongside. Nothing is estimated. The only figure that can be off is the acreage itself.

For a quick check in your head, multiplying acres by 0.4 comes out about 1.2% low, which is close enough to sanity-check a listing. Going the other way, hectares times 2.5 less 1% lands within about 0.2% of the true value.

The exact conversion factor

An acre is 43,560 ft², the area of one chain by one furlong (66 ft × 660 ft). A foot has been exactly 0.3048 m since 1959, so a square foot is 0.09290304 m² and 43,560 ft² comes to 4,046.8564224 m², with nothing rounded. Divide by 10,000 and you have the hectare factor, 0.40468564224. NIST's revised unit conversion factors list the acre at 4,046.856 422 4 m², the value this calculator uses. The result shows hectares to four decimal places (0.4047 ha for one acre) but the multiplication uses the full factor. To go from hectares back to acres, divide by 0.40468564224, or multiply by 2.4710538.

What a hectare actually measures

A hectare is a square 100 m on a side: 100 m × 100 m = 10,000 m². It is not strictly an SI unit, but the BIPM's SI Brochure lists it among the units accepted for use with the SI, and it is the standard unit of land area across most of the world. Farm statistics, forestry, land registries and planning documents in Europe, Latin America, Africa and much of Asia are kept in hectares. One hectare is about 2.471 acres, or about two and a quarter football fields without the end zones (each is 300 ft × 160 ft, about 4,459 m²).

What an acre actually measures

The acre started as roughly the land a team of oxen could plough in a day, laid out as a strip one furlong (660 ft) long and one chain (66 ft) wide. That is why the historical acre was a long, narrow strip. Today an acre is simply 43,560 ft² in any shape. A square acre has sides of about 208.7 ft (63.6 m), and a square lot, a long rectangle and an irregular field of the same area all convert the same way.

Acres, hectares, and square metres compared

One acre is 0.4047 ha, 4,047 m² and 43,560 ft². One hectare is 2.471 acres and 10,000 m². In the US, acres are the everyday unit for land: USDA's National Agricultural Statistics Service reports US crops in acres, and farm, ranch and rural listings are quoted that way. Most other countries, and international datasets such as the FAO's FAOSTAT, use hectares, and USDA's Foreign Agricultural Service also reports world crop area in hectares in its World Agricultural Production circular so it lines up with them. The calculator shows all three units at once, so a figure quoted in one reads straight across to the others.

Worked examples

A 2.5-acre rural lot is 1.0117 ha, or 10,117 m². Ten acres is 4.0469 ha. The US land-survey grid gives two more useful reference points: a quarter section of 160 acres is 64.7497 ha, and a full section of 640 acres, one square mile, is 258.9988 ha. Each of these comes straight from the single factor, with no rounding along the way.

Where the conversion comes up

US real estate quotes rural and larger suburban parcels in acres and smaller residential lots in square feet, and zoning codes and subdivision plats follow the same pattern. Federal permitting is in acres too: wetland impacts under Army Corps of Engineers permits and project areas in environmental impact statements are stated in acres. Hectares come in when the same land meets an international audience: a buyer or investor from abroad, a scientific paper, a carbon or forestry registry, or a dataset shared with other countries. Surveyors and GIS analysts moving data between US and international systems make this conversion constantly.

The acre is not only American. Farms and rural property in the UK and Ireland are still widely advertised in acres even though official records use hectares, older land titles in Canada and Australia were drawn up in acres, and acres remain in everyday use for farmland in parts of South Asia. Anyone comparing a listing in acres with a register, a grant scheme or a dataset in hectares needs the same single factor.

Precision and rounding

With no rounding in the factor, the result is as precise as the acreage entered, and the display rounds only for readability: hectares to four decimal places, square metres and square feet to the nearest whole unit. One wrinkle applies to older US records. Until the end of 2022 the acre was defined in US survey feet, which made it about 4 parts per million larger, roughly 0.016 m² per acre. NIST deprecated the US survey foot from January 1, 2023, so the acre is now defined in international feet. On a 1,000-acre ranch the difference is about 16 m² (174 ft²), far smaller than the uncertainty in most land surveys. For anything legal, the area on a measured survey or recorded plat counts, because the measurement, not the arithmetic, sets the real accuracy.

Using this alongside other BuildMetricLab tools

Once a land area is in square feet or square metres it reads straight into area-based tools: concrete slab coverage, artificial turf quantities, or a fence estimate for the boundary. The Acres to Square Feet calculator handles the same input in US customary units, and the Feet and Inches to Metres converter turns boundary lengths from a plat into metres. Every BuildMetricLab tool runs in your browser, with no sign-up and no data sent anywhere, and shows its formula so the math can be audited.