Acreage Calculator

How to calculate acreage

Find the area of the land in square feet, then divide by 43,560. That is the whole acreage formula: an acre is 43,560 square feet of land, whatever its shape.

Worked example: a field 660 feet long and 330 feet wide is 217,800 square feet. Divide by 43,560 and it holds exactly 5 acres. A lot 100 × 150 ft is 15,000 sq ft, or 0.34 acres.

Measured in yards, meters, chains or miles? Pick the unit in the acreage calculator and it converts every measurement to feet before it divides, so you never mix units by accident.

How to use the acreage calculator

The acreage calculator follows the same steps a surveyor's area check does, and shows each one in "How we calculated this" and in the PDF report.

Step 1: Pick the shape in the acreage calculator

Choose rectangle, four sides plus a diagonal, triangle, trapezoid or circle. If you already know the square footage from a plat or listing, choose "I know the sq ft" and the tool just converts it.

Step 2: Enter each dimension and its unit

Type the length of each side in feet, yards, meters, chains or miles. For a four-sided parcel, add the diagonal from the front-left corner to the back-right corner. The tool warns you when the sides cannot close into that shape.

Step 3: Add the asking price (optional)

Enter the total price of the land and the result adds the price per acre and per square foot, the two numbers buyers use to compare listings.

Step 4: Read the result in every unit

You get the total acreage, square feet, square yards, square meters and hectares at once, plus square miles for large parcels. Download the PDF report to keep the measurements with the result.

Acreage formulas for every land shape

Few properties are perfect rectangles. These are the exact formulas the calculator uses; each one gives square feet, which you then divide by 43,560.

Rectangle or square

Length × width. A square acre measures about 208.7 feet on each side, because 208.7 × 208.7 ≈ 43,560.

Four-sided lot with a diagonal

Most parcels are four-sided but have no right angle, so length × width over- or under-counts. Measure the four sides and one diagonal: the diagonal splits the quadrilateral into two triangles, and Heron's formula gives the area of each from its three sides.

Example: sides of 300, 420, 280 and 400 ft with a 540 ft diagonal make triangles of 62,684 and 54,398 sq ft, a total of 117,082 sq ft, or 2.69 acres.

Triangle

Heron's formula needs only the three sides: s = (a + b + c) ÷ 2, then area = √(s × (s − a) × (s − b) × (s − c)). Sides of 400, 350 and 300 ft enclose 50,833 sq ft, or 1.17 acres.

Trapezoid

When the front and back lines are parallel: (front + back) ÷ 2 × the depth between them. A lot 250 ft wide at the road, 350 ft at the back and 500 ft deep is 150,000 sq ft, or 3.44 acres.

Circle

π × radius², with the radius half the diameter. A round field 500 ft across covers 196,350 sq ft, or 4.51 acres. Center-pivot irrigated fields are the classic case.

Irregular land with more than four sides

Break it into rectangles, triangles and trapezoids, work out each piece, and add the acres. The square footage calculator adds several sections at once and sends the total back here.

How big is an acre?

An acre is a unit of area, not a shape. The US customary acre was defined as a strip one chain (66 ft) wide and one furlong (660 ft) long, the land a team of oxen could plow in a day: 66 × 660 = 43,560 sq ft. NIST Handbook 44 still lists the acre as 43,560 square feet, or 4,840 square yards.

• A football field: 360 × 160 ft with both end zones, 57,600 sq ft, or about 1.32 acres. Between the goal lines it is 1.1 acres.
• A quarter acre: 10,890 sq ft, a common suburban lot, roughly 75 × 145 ft.
• A half acre: 21,780 sq ft, about 147.6 ft on each side if it were square.

Acres to square feet, yards, meters and hectares

Exact conversions (43,560 square feet = 1 acre), with the side of a square parcel of the same size. Use them to check a listing or a deed at a glance.

How to measure land for an acreage calculation

Walk every boundary and write each side down before you calculate. A 100 ft tape works for a yard; a measuring wheel is faster over hundreds of feet; a GPS app or a satellite map gives a quick outline of a field.

Measure horizontal distances. Deeds and surveys record land as if it were flat, so a tape laid along a steep slope reads longer than the survey and the acreage comes out a little high. On hills, hold the tape level or use the map.

The survey foot and why acreage can differ slightly

Older US surveys used the US survey foot, about 2 parts per million longer than the international foot of 0.3048 m. NIST deprecated it from January 1, 2023. The difference is tiny for a house lot, but on thousands of acres it can move the last decimal of a legal description.

Price per acre

Land is compared by the price per acre, not the total price. Divide the asking price by the acreage: 12.5 acres listed at $150,000 cost $12,000 per acre. For small lots, the price per square foot is often more useful: the same land costs about $0.28 per sq ft.

Enter the price in the acreage calculator and both figures appear in the result. Compare parcels of similar size, since small parcels usually cost more per acre than large ones.

Land units in the US

Land is listed in acres in the US, but surveys, deeds and maps use other units too. These are the exact relationships:

• 1 acre = 43,560 sq ft = 4,840 sq yd = 0.4047 hectares = 10 square chains.
• 1 chain (Gunter's chain) = 66 ft = 4 rods; 1 furlong = 660 ft = 10 chains.
• 1 square mile = 640 acres. In the Public Land Survey System, one section of land is about a square mile, and a township holds 36 sections, about 23,040 acres.
• 1 quarter section = 160 acres, the size of a homestead claim in much of the West.
• 1 hectare = 10,000 m² = 2.471 acres. See the hectares to acres converter.

What an acreage calculation is used for

• Buying or selling land: check the listed acreage and the price per acre before you compare parcels.
• Farming and pasture: seed, fertilizer and lime rates are given per acre.
• Fencing and mowing: the acreage tells you how long the job takes; the perimeter tells you how much fence to buy.
• Building: residential lots are usually given in square feet; see the lot size to acres calculator for frontage × depth and lot coverage.

Common acreage mistakes

• Treating a four-sided lot as a rectangle. Without the diagonal, length × width can be off by a lot on a skewed parcel.
• Mixing units. Yards on one side and feet on another. Pick one unit for every side.
• Measuring along a slope. It inflates the area compared with the survey.
• Trusting a map outline for a legal boundary. Use it to estimate, not to build a fence on the line.

Before you rely on your acreage

Measure every side and the diagonal, keep one unit, and let the acreage calculator turn it into acres, square feet and hectares, with the price per acre if you add one. Compare the result with the deed or plat, download the PDF report, and call a licensed surveyor for anything legal.

Frequently asked questions