Calculate Acreage From Length, Width, or Area

Calculate acreage by dividing the measured land area in square feet by 43,560, or by converting another area unit to acres. Enter length and width in feet to estimate the area of a rectangular parcel; the calculator returns acres and square feet.

Formula

For a rectangular area, multiply its length by its width to find square feet, then divide by 43,560 square feet per acre:

Acres = length × width ÷ 43,560

• Length (l): one side of the measured rectangle, in feet.
• Width (w): the side perpendicular to the length, in feet.
• Area: length × width, in square feet.
• Acreage: area in square feet ÷ 43,560, in acres.

An acre is a unit of area, not a unit of length. One acre equals 43,560 square feet, 4,840 square yards, or about 4,046.86 square metres. In metric units, calculate square metres and divide by about 4,046.86 to obtain acres.

Worked Example

With the calculator’s default values, the rectangle is 200 feet long and 100 feet wide:

1. Area = 200 ft × 100 ft = 20,000 sq ft.
2. Acres = 20,000 ÷ 43,560 = 0.459136… acres.
3. Rounded to four decimal places, the result is 0.4591 acres.

The same area is 20,000 square feet, approximately 1,858.06 square metres, or about 0.186 hectares. The hectare conversion is useful when comparing measurements in metric contexts; one hectare is 10,000 square metres, or about 2.471 acres.

How to Measure and Calculate a Parcel

The length-times-width method applies directly when the measured land is rectangular and the sides meet at right angles. For a square, enter the same side length twice. For example, a square 100 feet on each side has 10,000 square feet, or about 0.2296 acres.

For a nonrectangular parcel, first determine its area using a suitable method, then convert that area to acres. A practical approach is to divide the outline into simple shapes, calculate each shape’s area, and add the results. For a triangle, use base × perpendicular height ÷ 2. For a trapezoid, use (first parallel side + second parallel side) × perpendicular distance between them ÷ 2. Keep all measurements in the same unit before adding areas.

• Measure boundaries in a consistent unit and record the units with the numbers.
• Sketch irregular outlines and break them into rectangles, triangles, or trapezoids.
• Calculate each section’s area, then add the section areas.
• Divide the total square feet by 43,560, or total square metres by 4,046.86.

For a large, uneven, sloped, or legally important parcel, simple side measurements may not describe the boundary or surface accurately. A map, survey, or professional measurement may be needed for a dependable figure. The calculator is a geometry aid, not a replacement for establishing property boundaries.

Choosing the Right Measurement

Use the dimensions of the area you actually want to measure. A property may include a house, driveway, pond, or other features; whether these are included depends on whether you are calculating the whole parcel or only usable land. The rectangle calculator treats the entered dimensions as a single continuous rectangle and does not subtract obstacles or account for boundary indentations.

Length and width must use matching units. If you measured in yards, convert each dimension to feet by multiplying by 3 before entering them. If dimensions are in metres, convert both to feet using 1 metre ≈ 3.28084 feet, or calculate the area in square metres and divide by 4,046.86. Do not multiply a measurement in feet by one in metres and treat the product as square feet.

A map scale can help estimate dimensions, but the result inherits any uncertainty in the map, scale reading, and boundary placement. Likewise, rounding each side before calculating can shift the final area. Keep reasonable precision during the calculation and round the acreage only at the end.

Common Errors and Limits

• Confusing acres with linear dimensions: acreage describes two-dimensional area; a length alone cannot determine it.
• Using 43,560 as a length conversion: it is the number of square feet in one acre, so it applies to area.
• Assuming every plot is rectangular: multiplying the longest and widest measurements can overstate an irregular parcel’s area.
• Mixing units: convert all lengths to the same unit before multiplying.
• Treating an estimate as a boundary survey: measurement and mapping errors affect the result, and this calculation does not verify ownership lines.

The displayed acreage is rounded to four decimal places. That is a numerical presentation choice, not a claim that the original dimensions are accurate to that level. If your measurements are approximate, report the result as an estimate and avoid implying more precision than the measurements support.

Frequently Asked Questions

How many square feet are in an acre?
One acre contains exactly 43,560 square feet. Divide a square-foot area by 43,560 to convert it to acres.

How do I calculate acres from feet?
For a rectangle, multiply its length in feet by its width in feet, then divide the result by 43,560. For an irregular shape, find its total area first.

How many acres is a 100-by-100-foot lot?
It is 10,000 square feet. Dividing by 43,560 gives approximately 0.2296 acres.

How many acres are in a hectare?
One hectare is about 2.471 acres. Conversely, one acre is about 0.4047 hectares.

Can I calculate acreage from a map?
Yes, if the map has a reliable scale and you measure the parcel outline consistently. The result is an estimate whose accuracy depends on the map and measurement method; a survey is more appropriate when precise boundaries matter.

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in l | Length | ft | 200 | 0
in w | Width | ft | 100 | 0
out acres | Acreage | acres | l * w / 43560 | 4
out area | Area | sq ft | l * w | 0