Acreage Calculator
Estimate the geometric area of a parcel by splitting it into simple measured sections. Add rectangles, triangles, trapezoids or circles, subtract only boundary notches that an oversized added shape included, and see one total in acres, hectares, square feet and square metres. The section breakdown makes every formula auditable. This is a planning estimate from your measurements, not a boundary survey, deed interpretation or statement of legal or buildable acreage.
How to calculate acreage from parcel measurements
-
1
Choose one length unit
Use feet, metres or yards consistently for every section. Mixing unconverted measurements produces the wrong area.
-
2
Split the parcel into shapes
Divide the plan into non-overlapping rectangles, triangles, trapezoids and circles that you can measure reliably.
-
3
Add or subtract each section
Add parcel sections. Subtract only an outside-boundary notch that an oversized added shape included; internal features remain part of parcel area.
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4
Review the converted total
The calculator sums in square metres internally, then converts the same total to acres, hectares and common square units.
Parcel-section formulas
An acre describes area, not a required shape. A one-acre parcel can be long and narrow, square, circular or an irregular combination of smaller sections.
| Shape | Measurements required | Area formula |
|---|---|---|
| Rectangle | length and width | A = L × W |
| Triangle | base and perpendicular height | A = b × h ÷ 2 |
| Trapezoid | two parallel sides and perpendicular height | A = (a + b) × h ÷ 2 |
| Circle | radius | A = πr² |
The triangle and trapezoid height must be perpendicular to the base or parallel sides. A sloping side is not the height unless it meets that condition.
Exact acreage conversions
This calculator uses the international foot and these exact relationships:
| Area | Exact equivalent |
|---|---|
| 1 acre | 43,560 ft² |
| 1 acre | 4,840 yd² |
| 1 acre | 4,046.8564224 m² |
| 1 acre | 0.40468564224 ha |
| 1 hectare | 10,000 m² |
| 1 square mile | 640 acres |
Values are kept at full precision during the calculation and rounded only for display.
Worked example: one acre
A rectangle measuring 660 ft by 66 ft has:
660 × 66 = 43,560 ft²
Because 43,560 square feet is exactly one acre, the same parcel is approximately 0.404686 hectares or 4,046.8564224 square metres.
Estimating an irregular parcel
Suppose a parcel plan can be represented by:
- a 200 ft × 150 ft bounding rectangle; and
- a triangular boundary notch outside the parcel with a 90 ft base and 40 ft perpendicular height.
Calculate the oversized rectangle, subtract the measured notch that lies outside the actual boundary, and then convert the net square area. Do not subtract a pond, wetland, easement or setback inside the boundary: those may affect usable land, but they normally remain part of the parcel’s geometric acreage.
Why four sides are not enough
Four side lengths alone do not determine one unique quadrilateral area. Different angles can produce different areas with the same four sides. Divide the parcel into measured triangles or other simple shapes, or use a qualified map/GIS workflow with ordered coordinates. Avoid “average opposite sides” shortcuts when accuracy matters.
Horizontal area, legal acreage and usable land
The formulas estimate horizontal plan area. Tape measurements taken along a steep slope can be longer than the horizontal distance and overstate the plan area.
Recorded acreage can also differ because of boundary monuments, curves, coordinate systems, historic survey units or later surveys. Easements, setbacks, rights-of-way, wetlands and other restrictions normally affect usable or buildable land; they do not automatically change the geometric parcel area.
For a purchase, dispute, subdivision, tax matter, construction near a boundary or any legal use, check the deed and plat and consult a licensed land surveyor or the appropriate local professional.
Sources and standards
Frequently Asked Questions
One international acre is exactly 43,560 square feet. It is also exactly 4,840 square yards and 4,046.8564224 square metres.
Split it into non-overlapping simple shapes you can measure, calculate each area, then add them. Use subtraction only for a measured notch outside the true boundary that was included by an oversized added shape.
Not uniquely. Four side lengths can form different shapes with different areas. You need additional information such as angles, a diagonal or ordered coordinates, or you can divide the parcel into measurable triangles.
No. It estimates geometric area only. Setbacks, easements, rights-of-way, wetlands, access and zoning can reduce usable or buildable land without changing the parcel’s geometric acreage.
No. Legal boundaries depend on records, monuments and professional survey methods. Use the calculator for planning estimates and consult a licensed surveyor for legal, purchase, construction or dispute decisions.
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