Acreage Calculator

Miscalculating land area by even a small margin compounds into significant financial error. A 1% measurement mistake on a 40-acre parcel means roughly 0.4 acres - at $10,000 per acre that is $4,000 lost or overpaid. This calculator converts raw dimensions into acreage using the definition 1 acre = 43,560 ft², a standard codified by the International Yard and Pound Agreement of 1959. It handles six geometric shapes and accumulates multiple sub-plots into a single total. All inputs are converted to square feet internally before the acre division, so you can mix units freely across plots.

The tool assumes flat, two-dimensional measurement. Sloped terrain requires a cosine correction factor that depends on grade angle. For legal land transactions always cross-reference with a licensed surveyor's plat; this calculator provides planning-grade estimates assuming level ground and ideal geometry. Pro tip: GPS-derived coordinates can drift 2 - 5 m, so for parcels under 1 acre, tape-measure dimensions yield better accuracy.

The core conversion factor is defined as:

For a rectangular plot the area in acres is:

where L = length in feet and W = width in feet.

For a triangular plot:

where b = base length and h = perpendicular height.

For a circular plot:

where r = radius in feet.

For a trapezoidal plot:

where a and b are the two parallel sides and h is the perpendicular distance between them.

For an elliptical plot:

where a = semi-major axis and b = semi-minor axis, both in feet.

When input units are not feet, dimensions are first multiplied by the appropriate conversion factor (e.g., 1 m = 3.28084 ft) before applying the formulas above.