Acreage Calculator – Land Area in Acres

Find Lot or Field Area from Its Dimensions

Acreage Formula

Formula

\[\begin{aligned} s&=\frac{a+b+c}{2}, & H(a,b,c)&=\sqrt{s(s-a)(s-b)(s-c)} \\ \text{Area (acres)}&=\frac{1}{43{,}560}\begin{cases} AB & \text{rectangle}\\ H(A,B,C) & \text{triangle}\\ \pi A^2 & \text{circle}\\ H(A,B,d)+H(C,D,d) & \text{quadrilateral} \end{cases}\\ \text{Estimated land value}&=\text{area (acres)}\times\text{price per acre} \end{aligned}\]

Where:

$A$, $B$, $C$, and $D$ — the required lengths or consecutive boundary sides, converted to feet; $A$ is the radius for a circle.
$d$ — the quadrilateral’s measured diagonal, in feet.
$H(a,b,c)$ — the area in square feet of a triangle with sides $a$, $b$, and $c$; $s$ is its semiperimeter.

The calculator finds area in square feet, then divides by 43,560 to obtain acres. For a quadrilateral, the specified diagonal divides the lot into two triangles whose areas are added.

Acreage – Calculation Example

Example: a rectangular lot is 220 ft long and 198 ft wide. The price is $25,000 per acre.

\[\begin{aligned}\text{Area}&=220\times198=43{,}560\ \text{sq ft}\\\text{Area in acres}&=43{,}560\div43{,}560=1\ \text{acre}\\\text{Estimated land value}&=1\times\$25{,}000=\$25{,}000\end{aligned}\]

Result: 1 acre (43,560 sq ft), with an estimated land value of $25,000.

How to use the calculator

Choose Lot shape: Rectangle, Triangle (three sides), Circle, or Irregular quadrilateral. The fields needed for that shape will appear.
Enter Length / side 1 / radius (A). Use the radius—not the diameter—for a circle.
For a rectangle, triangle, or quadrilateral, enter Width / side 2 (B). For a triangle or quadrilateral, also enter Side 3 (C).
For an irregular quadrilateral, enter Side 4 (D) and Diagonal (d). Number sides A through D consecutively around the boundary. Measure the diagonal from the corner between A and D to the corner between B and C.
Select the Unit beside each dimension. The choices are ft, yd, m, rods, and chains; you may mix units.
Enter Price per acre (optional) to estimate land value, or clear that field to omit the estimate. Read the area in acres, sq ft, sq m, hectares, and sq miles under Land Area and Value.

What acreage tells you

Acreage measures the area within a land boundary, rather than the length of its edges. One acre equals 43,560 square feet, or approximately 4,046.86 square meters. The same area can describe a long, narrow parcel or a nearly square one, so acreage alone does not describe a lot’s shape or frontage.

The shape determines which measurements are sufficient. Length and width define a rectangle; a radius defines a circle. Three side lengths define a triangle when they can form one. Four side lengths alone generally do not fix a quadrilateral’s area: its corners can move while those lengths stay the same. The additional diagonal fixes the two triangles used by this calculator.

The results show one area in several units, not separate measurements. The estimated land value is simply acreage multiplied by the entered price per acre. It can help compare parcels at a common rate, but it is not an appraisal: access, location, permitted use, improvements, and other factors may affect a sale price.

Measurement assumptions and practical tips

Enter positive dimensions. For each triangle, the sum of any two sides must exceed the third. This also applies to both triangles formed by a quadrilateral’s diagonal; otherwise, the calculator cannot produce an area.
For a quadrilateral, confirm that the measured diagonal runs through the parcel’s interior and divides it into triangles with sides A–B–d and C–D–d. A different diagonal or incorrect side order can produce a different result.
Rectangular and circular calculations assume the boundary matches the selected shape. For an uneven field, divide it into measurable sections and add their areas, or use surveyed boundary data.
Use horizontal ground dimensions for land area. A distance measured along a steep slope can be longer than its horizontal distance and may overstate the result.
Surveyed acreage may differ from a measurement-based estimate because of boundary detail, measurement precision, or legal descriptions. Use a qualified surveyor when an exact property boundary matters.

Checking and using the result

For a quick check, a 66 ft by 660 ft rectangle is exactly one acre. A chain is 66 ft and a rod is 16.5 ft, so these older land-measurement units can be entered directly. If you already know an area rather than its dimensions, use the square feet to acres converter or the acres to square meters converter. To estimate how much water falls on a measured area, see the rainfall volume calculator.

Frequently Asked Questions

How can I calculate acreage by hand for a lot with an unusual shape?

Break the lot into rectangles and triangles, calculate each area, and add them together. For a triangle with a known base and perpendicular height, multiply the base by the height and divide by two. Keep all measurements in the same length unit, then convert the total area to acres. This gives an estimate if the sections only approximate the boundary.

How big is a quarter-acre lot in feet?

A quarter acre contains 10,890 square feet. If it is square, each side is about 104.4 feet long. It could instead be a rectangle measuring 66 feet by 165 feet. Both have the same area, so the acreage alone cannot tell you a lot’s dimensions.

How many acres are in a hectare or a square mile?

One hectare is approximately 2.471 acres, and one square mile is exactly 640 acres. To convert hectares to acres, multiply by 2.471; to convert square miles to acres, multiply by 640. These are area conversions—do not apply a length conversion factor directly to an area.

What is a good lot size for a house?

There is no universally good acreage for a home. A smaller lot may suit a low-maintenance home, while a larger one may provide room for setbacks, a septic system, gardening, or outbuildings. Check local zoning, utility access, easements, and building restrictions before deciding whether a parcel meets your needs.

Can I find a lot’s acreage from its perimeter?

No. Perimeter alone does not determine area. For example, a 100-by-100-foot rectangle and a 50-by-150-foot rectangle both have a 400-foot perimeter, but their areas are 10,000 and 7,500 square feet. You need dimensions that establish the shape, an area measurement, or boundary data.

Is the entire acreage of a parcel usable?

Not necessarily. The total parcel area may include wetlands, steep terrain, easements, required setbacks, or land subject to other restrictions. Those conditions can reduce the space available for a particular project without changing the parcel’s acreage. For a purchase or building plan, check the survey and local rules rather than treating total acreage as buildable acreage.

How do I convert a price per square foot to a price per acre?

Multiply the price per square foot by 43,560. For example, $2 per square foot equals $87,120 per acre. Check that both prices refer to comparable land: a quoted price might include a house or other improvements. A rate conversion is useful for comparison, but it does not establish a property’s market value.