Hectares to Acres Converter

hectares to acres — quick reference

The formula

A hectare is exactly 10,000 m², the area of a square 100 m on a side. An acre is 4,840 square yards, and since the international yard has been exactly 0.9144 m since 1959, that is exactly 4,046.8564224 m². Dividing one by the other gives a factor with no approximation in its definition, only in how many decimals you choose to print.

The reciprocal does not terminate — 2.47105381467165 and on — which is why every published acre-per-hectare figure is a rounded one while the hectare-per-acre figure, 0.40468564224, is exact. Dividing by the exact number is therefore slightly better practice than multiplying by a truncated 2.4711, though the difference only shows up on large totals.

acres = hectares ÷ 0.40468564224
      = hectares × 2.4710538…
      = hectares × 10,000 m² ÷ 4,046.8564224 m²
square miles = hectares ÷ 258.9988

Worked example with the default: 1 ÷ 0.40468564224 = 2.4710538 acres, displayed as 2.47 — one hectare is a shade under two and a half acres. Scale it up and the pattern is clean: 100 ha is 247.1054 acres and is also exactly one square kilometre, 500 ha is 1,235.53 acres, and 10,000 ha is 24,710.54 acres. Push it into the unit that actually communicates and 10,000 ha is 38.6 square miles, because 258.9988 ha make a square mile.

The multiply-by-2.5 shortcut reads 1.17 percent high, since the true factor is 2.4711. On 5 ha it adds about 0.15 of an acre and nobody cares. On 500 ha it gives 1,250 acres against a true 1,235.53, inventing nearly 15 acres, and on a 10,000-hectare figure it invents 289. The error always points the same way — upward — so it consistently flatters whatever it is applied to, which makes it the wrong direction to be wrong in if you are estimating how much land you are buying or how much has burned.

One caution about the source numbers rather than the arithmetic. Reported hectare totals for fires, deforestation and land use are often preliminary, are frequently revised, and may measure different things: a fire perimeter is not the same as the area actually burned inside it, and a cleared-area statistic may or may not include degraded forest. Converting such a figure to four decimal places gives it a precision the original never had. Convert faithfully, then present the result at roughly the same precision as the input — 24,700 acres, not 24,710.5381.

How to use the hectares to acres converter

Hectares reach US readers through data rather than deeds. Farm and crop statistics, conservation and reserve areas, vineyard and orchard sizes, deforestation totals, and wildfire figures from abroad are all reported in hectares. Enter the metric number and this converter gives you acres, the unit US land is actually bought and sold in; Swap runs it the other way. The factor is exact rather than approximate, since a hectare is exactly 10,000 m² and an acre is defined as 4,840 square yards, which at the exact 0.9144 m yard makes it exactly 4,046.8564224 m². Dividing one by the other gives 2.47105381 and change, with no measurement uncertainty anywhere in it.

Start with the anchors. One hectare is 2.47 acres, 10 ha is 24.71 acres, and 100 ha — which is exactly one square kilometre — is 247.11 acres. Going up, 500 ha is 1,235.53 acres and 1,000 ha is 2,471.05 acres. The single most useful equivalence is that 259 ha is one square mile, because a square mile holds 640 acres and 640 times 0.40468564 is 258.9988. Once you have that, any large metric area converts into a shape you already know: 2,590 ha is ten square miles, 25,900 ha is a hundred, and anything reported as a round number of square kilometres divides by 2.59 to give square miles directly.

It matters most when a headline number is doing the work, because a hectare total in a news report is a figure almost no American reader can size. A wildfire reported at 10,000 hectares has burned 24,711 acres, or about 38.6 square miles. One at 100,000 hectares has covered 386 square miles, which is larger than many US cities. A 500-hectare estate is 1,236 acres. A 20-hectare vineyard is 49.4 acres, and a 50-hectare orchard is 123.6 acres. For a physical reference at the small end, a hectare is about one and a half football pitches at 105 m by 68 m, or roughly two American football fields including their end zones.

The shortcut is to multiply hectares by 2.5, or to halve the number and add double the half, which comes to the same thing. It runs 1.17 percent high: one hectare gives 2.5 acres against a true 2.4711, and 100 ha gives 250 against 247.11. That is fine for reading a news figure, but at 10,000 ha the shortcut has invented 289 acres out of nothing, and the error always points upward, so it flatters whatever you are measuring. Switch to the exact factor for anything reported, transacted, or compared. And for very large areas, do the second conversion into square miles as well, since 247,105 acres is just as unpicturable as the hectares it came from.

Every hectares value, worked out

57 common hectares figures each get their own page, with the answer at full precision, the arithmetic, what rounding costs, and the nearest real-world reference point on the scale.

Frequently asked questions