Acres to Hectares conversion

Acres to hectares

Land measured in acres — an American farm, a British estate, a Canadian lot — often has to be reported in hectares for official, scientific or international purposes. One acre is 4 046.86 square meters, which makes it 0.404686 hectare. Multiply acres by 0.404686, or divide by 2.47105.

Rule of thumb

Take 40 % of the acres: 50 acres ≈ 20 ha (20.2 exactly), 250 acres ≈ 100 ha (101.2). It undershoots by about 1 %, which is fine for a first look at a listing.

• 1 acre = 0.4 ha
• 2.5 acres = 1.01 ha (almost exactly one hectare)
• 5 acres = 2.02 ha
• 10 acres = 4.05 ha
• 40 acres = 16.19 ha
• 100 acres = 40.47 ha
• 640 acres = 259 ha (one square mile)
• 1000 acres = 404.69 ha

History in the number

The acre was the area a yoke of oxen could plough in a day: one furlong long by one chain wide, 660 ft × 66 ft. The hectare was defined in 1795 as a neat 100 m × 100 m square. That is why the conversion factor is an awkward decimal — the two units come from different worlds.

Practical notes

Farming. Seeding and fertiliser rates on North American product labels are per acre; European labels are per hectare. Multiply a per-acre rate by 2.47 to get the per-hectare rate. Real estate. A "10-acre property" abroad is a 4-hectare property. Forestry and conservation. International reports (FAO, UNEP) always use hectares, so US figures are converted before publication.

Worked examples

A 160-acre farm (a quarter section). 160 × 0.4047 = 64.7 ha.

A 1-acre garden. 0.4047 ha, or 4 047 m² — a square about 64 m on a side.

Fertiliser at 50 lb per acre. 50 × 0.4536 kg ÷ 0.4047 ha = 56 kg per hectare.

Frequently asked questions

How many hectares are in an acre? 0.4047. Ten acres are about 4 hectares.

How many acres make a square mile? 640. That is 259 hectares or 2.59 km².

Why 43 560 square feet? An acre is a chain (66 ft) by a furlong (660 ft), and 66 × 660 = 43 560.

Related conversions

Hectares to acres reverses this page. Acres to square feet gives the building-scale figure, and square feet to square meters completes the chain into metric.

Good to know

Because the acre came from ploughing and the hectare from surveying, the two units are used differently on the ground. Acres are rarely subdivided decimally in practice: American and British deeds describe land as "40 acres, more or less" and small plots as fractions of an acre. Hectares are used with decimals everywhere: a 2.35 ha field is perfectly normal. When converting a legal description, keep at least two decimal places in hectares, because 0.01 ha is 100 m², the size of a small house. Land registries in metric countries also use the "are" — 100 m², a hundredth of a hectare — so a plot of 12.5 ares is 0.125 ha, or 0.31 acre.