Acreage Calculator
Acreage calculator works out Area and Area unit from Shape, Length / base / side a and Width / second base / side b. The default figures on this page give area of 78.539816; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
5 steps
- Shape: Circle. Dimensions are in m.
- Formula: A = pi r^2.
- Area = 78.53981633974483 m2.
- In SI: 78.53981633974483 m^2 (= 845.3955472258481 sq ft).
- Perimeter = 31.41592653589793 m.
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
4 sources
What the acreage calculator calculates
Calculates the area and perimeter of any named plane shape - square, rectangle, triangle, parallelogram, rhombus, kite, trapezoid, circle, semicircle, ellipse, annulus, sector, segment or regular polygon - in any length unit, with the result convertible to any area unit.
How to use this acreage calculator
Enter Shape, Length / base / side a, Width / second base / side b and Perpendicular height. Area updates as you type, and “Use a worked example” loads checked figures you can adjust. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Area, Area unit and Area in square metres.
The method follows CRC Standard Mathematical Tables and Formulae, Geometry: areas and perimeters of plane figures, Weisstein, Eric W. "Area", MathWorld, S. Ramanujan, "Modular equations and approximations to pi", Quart. J. Pure App. Math. 45, 350-372, equation (2) for the ellipse perimeter and NIST Special Publication 811, Guide for the Use of the International System of Units (unit conversions).
Circle of radius 5 m example
With Shape: circle, Radius: 5, Unit of the dimensions: m, the calculator returns Area: 78.5398163, Area in square metres: 78.5398163, Perimeter: 31.4159265. This example is checked against an independent source in the test suite.
What you can compare
Change one input at a time to see how it affects Area, Area unit and Area in square metres. The inputs you can vary are Shape, Length / base / side a, Width / second base / side b, Perpendicular height, Side c and Radius.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How do I calculate the acreage of my property?
Calculates the area and perimeter of any named plane shape - square, rectangle, triangle, parallelogram, rhombus, kite, trapezoid, circle, semicircle, ellipse, annulus, sector. Open “How this is worked out” beside the result to see each step for your own figures.
Is there a way to estimate acreage on Google Maps?
Calculates the area and perimeter of any named plane shape - square, rectangle, triangle, parallelogram, rhombus, kite, trapezoid, circle, semicircle, ellipse, annulus, sector. On the figures this page opens with — radius 5 — the area is 78.539816. Put your own figures in their place and the working updates beside the result.
What information do I need for the acreage calculator?
You need Shape, Length / base / side a, Width / second base / side b, Perpendicular height, Side c, Radius, Inner radius and Diagonal p. The page opens with default figures that give area of 78.539816, so you can see the scale before entering your own.
What does this acreage calculator show?
It shows Area, Area unit, Area in square metres, Area in square feet, Perimeter, Perimeter unit, Shape and Formula used, with the working and any warnings for your entries.
Can I check how the acreage calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.