Acreage Calculator

The acre is one of the oldest continuously used units of measurement in the English-speaking world, and it's the primary unit for buying, selling, taxing, farming, and developing land across the United States, Canada, the United Kingdom, and Australia. Despite the global metric push, the acre remains deeply embedded in property deeds, county records, MLS listings, USDA farm programs, hunting-lease contracts, and timber-harvest plans. Whether you're buying rural land, planning a subdivision, running cattle, applying for crop insurance, or simply wondering how big your suburban lot really is, this calculator handles every shape and unit you'll ever encounter.

Originally an acre was the amount of land a yoke of oxen could plow in a day. Medieval England formalized it as 1 chain (66 ft) by 1 furlong (660 ft) — a clean 43,560 sq ft. That figure now anchors the US Public Land Survey System (PLSS), which divides the western US into 36-square-mile townships of 36 sections at 640 acres each: half-section (320 ac), quarter-section (160 ac), quarter-quarter (40 ac, the famous "back 40"). Outside the US, the hectare reigns — 10,000 sq m (a 100 m × 100 m square), about 2.47 acres. Our calculator shows acres and hectares side-by-side so you can translate any US listing to a European buyer or price Brazilian farmland in USD per acre without a separate converter.

The Formulas Behind Every Shape

This calculator supports six area modes, each with its own formula. Once each shape's area is computed in square feet, dividing by 43,560 gives acres.

The polygon formula — called the Shoelace formula or the Surveyor's Formula — is the workhorse for irregular land. List the (x, y) coordinates of each corner in order around the perimeter (we support up to 8 vertices), and the formula returns the exact area. It works for any simple (non-self-intersecting) polygon and is the same algorithm used by professional GIS systems like ArcGIS and QGIS. The result is mathematically exact for flat (planar) coordinates, which is more than accurate enough for any residential or small commercial parcel.

How to Use This Calculator

1. 1. Pick a Preset or Shape: Tap a quick lot preset (1 acre, ½ acre, ¼ acre, 5/10/40 acres) to auto-fill a rectangle, or pick a shape type — Rectangle, Triangle, Circle, Trapezoid, Polygon, or Direct sq ft / sq m.
2. 2. Enter Dimensions: Type lengths, widths, radii, or polygon vertex coordinates. Each shape has its own unit toggle so you can mix feet, yards, and meters across multiple shapes without errors.
3. 3. Add Multiple Shapes: For irregular lots, combine simple shapes — e.g., a rectangle for the main parcel plus a triangle for the road cut-off — and the calculator sums them. Up to any reasonable number of shapes is supported.
4. 4. Set Your Output Unit: Pick acres, sq ft, sq yd, sq m, hectares, or sq miles as the primary display. All other units are always shown alongside for cross-reference.
5. 5. Add a Price per Acre (optional): Type any per-acre dollar value to instantly compute total land value, perfect for real estate offers, comparable-sales analysis, or budget planning.

Common Use Cases

Pro Tips for Accurate Acreage

• • Use Google Earth for perimeter: Google Earth Pro's polygon tool gives perimeter and area on satellite imagery — cross-check with our Shoelace mode using the same vertex coordinates.
• • Start from a surveyor's marker: Concrete monuments, iron pins, and rebar set by the original surveyor are the legal corners of your lot. Always tie back to at least one official marker.
• • Lot vs. usable acreage: Wetlands, easements, road right-of-ways, and steep slopes count toward total acreage but may be unbuildable. List separate shapes for usable vs. constrained areas.
• • Watch for encumbrances: Power-line easements, oil & gas right-of-ways, and conservation easements can reduce effective acreage 10-30% without changing deed acreage. Always read the title commitment.
• • Walk the line clockwise: The Shoelace formula gives a signed area. We take the absolute value automatically, so order doesn't change the answer — but stay consistent for centroid calcs.
• • Verify against county records: Most US counties publish a free online parcel viewer with official acreage. If your calculator disagrees by more than 2%, investigate before relying on either number.

Whether you're buying a city lot or a quarter-section ranch, hunting a 200-acre lease or planning a 10-acre subdivision, this calculator turns any combination of shapes, units, and conversions into a single confident acreage number. Common reference sizes: ¼ acre (≈104×104 ft suburban lot), ½ acre (≈148×148 ft), 1 acre (208×208 ft), 5 acres (467×467 ft), 10 acres (660×660 ft), 40 acres (1320×1320 ft, the "back 40" PLSS aliquot), 160 acres (a quarter section), and 640 acres (a full section, one square mile). Bookmark this calculator, share it with your surveyor or real estate agent, and use it whenever a land deal lands on your desk.