Acreage & Land Area Calculator
Acres, hectares, m² and ft² of a parcel from a rectangle, a triangle by three sides, a circle, or corner coordinates of any polygon (shoelace), with perimeter.
The area of a lot or field in every unit a deed, a seed bag or a fencing quote uses — from the measurements you have, including an irregular boundary walked corner by corner.
Example: 660 × 330 ft is exactly 5 acres (2.023 ha, 20,234 m²). A four-corner lot at (0,0), (200,0), (200,150), (0,100) ft encloses 25,000 ft² = 0.574 acres with 656 ft of boundary.
An acre is 43,560 square feet.
The shape is the only question.
The four ways to give a parcel, how an irregular boundary is handled, and what a flat calculation leaves out.
Regular shapes
A rectangle is length × width. A triangle with three known sides uses Heron's formula, √(s(s−a)(s−b)(s−c)) with s the half-perimeter — and the page refuses sides that cannot close (one side longer than the other two together). A circle is π × D² ÷ 4 from its diameter. The perimeter is shown alongside because fencing, hedging and boundary work are priced by length.
Irregular parcels from corner coordinates
Any simple polygon — a lot with five or six sides, a field that follows a road — is handled by the shoelace formula: list the corners in order around the boundary as x, y offsets from any origin (paced, taped or read from a plan), and the area is half the absolute sum of x₁y₂ − x₂y₁ around the loop. The result is exact for the coordinates given; the corners must be in walking order and the sides must not cross, which the page reminds you of. Coordinates can be positive or negative and the origin is arbitrary.
Units
An acre is exactly 43,560 ft² (a chain by a furlong); with the international foot of 0.3048 m that is 4,046.856 422 4 m². A hectare is 10,000 m² (2.471 acres); a square mile is 640 acres. The page also gives the side of a square of the same area, a useful sanity check — 5 acres is a square about 467 ft on a side.
Limits
All geometry is on a flat plane. Sloping ground has a larger surface than its plan area, and legal acreage is the plan area from the surveyor's plat or deed, which governs over any calculation here. Latitude/longitude corners need a map projection before their coordinates can be used and are not accepted directly. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.
SOURCES
- NIST Special Publication 811 (2008), Guide for the Use of the SI, Appendix B — acre 4,046.856 422 4 m² (based on the international foot), hectare 10,000 m²
- Shoelace (surveyor’s) formula for the area of a simple polygon from vertex coordinates; Heron’s formula for a triangle from its sides — standard plane geometry
Last reviewed 19 September 2026. How results are checked: How we verify.