The acre(ac) is a unit of land area used in the imperial and US customary systems while a square mile(sq. mi) is a unit of area measurement equal to a square measuring one mile on each side.
Formula to convert sq. mi to ac.
To convert sq. mi to acres, we need to know the conversion ratio which we get from how they relate to each other.
We are told that 1 sq. mi is equal to 640 acres.
Therefore, to convert sq.mi to acres, we multiply the sq. mi value by 640.
Area in acres = Area in sq. mi x 640
Convert 400 mi² to acres.
= 400 x 640
= 256,000 acres.