Acres to hectares Converter

How many hectares are in a acre?

One acre is 0.404686 hectares. The full conversion is hectares = acres × 0.4046856422, and going the other way you divide instead of multiply.

A few anchor values worth memorising: 0.404686 ha to the acre, 4.046856 ha to ten, and 40.468564 ha to a hundred. The calculator above handles the rest, including the awkward decimals.

The reference table under the converter lists the values people look up most often, so for a common figure you can read the answer off directly rather than typing anything.

Worked examples

Three worked examples, each multiplying by 0.40468564:

2.5 ac × 0.404686 = 1.0117 ha. 25 ac × 0.404686 = 10.1171 ha. 250 ac × 0.404686 = 101.1714 ha.

To reverse any of them, divide instead of multiplying — or use the swap button above, which does the same thing without the arithmetic. Reversing a converted value should return you to exactly what you started with; if it does not, something has been rounded too early.

Doing this conversion in your head

The exact factor is 0.40468564, which nobody multiplies by in their head. It is very close to 2/5, so multiplying by 2 and dividing by 5 lands within 1.16% of the correct answer — accurate enough for anything short of engineering work.

Since the factor is less than one, the number always gets smaller: a acre is larger than a hectare, so any quantity converts to fewer of them. A result larger than what you started with means the conversion went the wrong way.

That sanity check catches the majority of real conversion errors. Before trusting any converted figure, ask whether the direction of change makes sense — it takes a second and it is the single most effective safeguard there is.

When you need to convert acres to hectares

This conversion tends to come up for a specific reason, and the reason usually decides how carefully you should round.

On the source side, acres describe farmland, building plots and land sales in the US and UK. On the target side, hectares are the international unit for farmland, forestry and land-use statistics. The conversion is essentially a translation between those two worlds — most often because a figure produced in one context has to be understood, submitted or acted on in the other.

Where the converted figure will be cut, dosed, billed or filed, round once at the end rather than at each step. For a rough sense of scale, round freely.

None of this leaves your browser. The conversion is a few lines of arithmetic, so there is no server involved and nothing to store.

What a acre and a hectare actually are

The acre (ac). Historically the land one ox team could plough in a day; now exactly 43,560 square feet.

The hectare (ha). 10,000 square metres — the international unit of farmland.

Because both measure area and their definitions are set by standards bodies, the factor between them never changes. It is not an approximation that improves with better instruments; it is a definition.

Common mistakes when converting acres to hectares

Acres are not square anything, which trips people up. An acre is 43,560 square feet in any shape — historically it was a long, thin strip about 66 feet by 660 feet, sized to what one team of oxen could plough in a day. A hectare, by contrast, genuinely is a square: 100 metres on a side.

If you are converting many values, change the source unit in the dropdown rather than converting through an intermediate unit. Every extra hop is another rounding opportunity.