There are 43,650 square feet in an acre, so a quarter of an acre is one-fourth of that, or 10,912.5 square feet. Since there are 4,840 square yards in an acre, a quarter-acre is also defined as 1,210 square yards of land.
Dimensions of quarter-acre lots vary. Square footage is calculated by multiplying the lot length by its width to arrive at the square footage. If the resulting number equals 10, 912.5 square feet, it is truly a quarter-acre lot. Quarter-acre lots inevitably vary in dimension (length times width), but any combination of calculated dimensions count toward the total square footage.