Area Calculator
Calculate the area of rectangles, triangles, circles, trapezoids, ellipses and sectors.
About Area Calculator
Area measures the two-dimensional space enclosed by a shape. Rectangle area is length × width. A triangle is half the base times the height. A circle is πr². A trapezoid uses the average of the two parallel sides times the height. An ellipse generalises the circle formula using its two semi-axes. A sector is a fraction of a full circle's area determined by the central angle. A parallelogram is base times perpendicular height.
Formulas
Rectangle
A = length × width
Triangle
A = ½ × base × height
Circle
A = π × r²
Trapezoid
A = ½ × (a + b) × height
Ellipse
A = π × semi-major × semi-minor
Sector
A = (θ/360°) × π × r²
Parallelogram
A = base × height
Worked example
With the default values below, Area Calculator returns Area of 40.000000. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Shapeone of Rectangle, Triangle, Circle, Trapezoid, Ellipse, Sector, Parallelogram
- Rectangle
- Lengthminimum 0
- 8
- Widthminimum 0
- 5
- Baseminimum 0
- 6
- Heightminimum 0
- 4
- Radiusminimum 0
- 5
- Base 1 (a)minimum 0
- 6
- Base 2 (b)minimum 0
- 4
- Heightminimum 0
- 3
- Semi-major axis (a)minimum 0
- 7
- Semi-minor axis (b)minimum 0
- 4
- Radiusminimum 0
- 5
- Central angle (degrees)accepts 0–360
- 90
- Baseminimum 0
- 8
- Height (perpendicular)minimum 0
- 5
Results
- Area
- 40.000000
- Shape
- Rectangle
Step by step
- 1Formula
- 2Substitute
- 3Area= 40
Assumptions and limits
- The result is derived only from the 15 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 6 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
What's the difference between area and perimeter?
Area is the space inside a shape, measured in square units (cm², m², ft²). Perimeter is the total length of the boundary, measured in linear units (cm, m, ft).
Why does a triangle's area formula have ½?
A triangle is exactly half of a parallelogram (or rectangle) with the same base and height. You can see this by duplicating any triangle and fitting the copy alongside the original to form a parallelogram.
How do I find the area of an irregular shape?
Divide it into simpler sub-shapes whose areas you can calculate, then add them up. Alternatively, use the Shoelace formula if you know all the vertex coordinates.