Acres to square meters (acre to m2)

One acre is exactly 4,046.856422 square meters. That is a definition rather than a measurement: the imperial and US customary units were fixed against metric ones by the 1959 international yard and pound agreement, so this factor does not drift and will not be revised.

Worked through: 2 acre x 4,046.85642 = 8,093.71 m2.

Going the other way, one square meter is 0.0002471054 acres.

For mental arithmetic: Multiply by 4,000 and add 1.2%.

One acre is 4,046.8564224 square meters, which is exact but deeply unround: it is 4,840 square yards, and a yard is 0.9144 meters, so the metric figure inherits every digit of that definition. The hectare exists to be the round alternative: 10,000 square meters, which is 2.471 acres. Agricultural land is quoted in hectares almost everywhere except the US, UK and a few others, so this conversion and the acre-to-hectare one are what cross-border land comparisons run on.

Precision is worth matching to the input. A measurement given as 0.25 acre carries one or two significant figures, and reporting its conversion to six implies a precision the original never had.