# Area Calculator – Find the Area of 10 Geometric Shapes

Calculate the area of a shape by selecting a shape and entering your measurements in any unit, metric or imperial. See formulas for each shape below.

Select a Shape:

## How to Find Area

Area is the space inside the perimeter/boundary of a space and can be symbolized as (A). It’s the size of a 2-dimensional surface and is measured in square units, for example. square feet. Square feet can also expressed as ft2. Use our formulas to find the area of many shapes.

It’s important to measure all lengths in the same unit of measure or to convert all lengths to the same unit before calculating area. Our length unit conversion calculators can be used to convert your length from one unit to another. Our area unit conversion calculators can also convert an area measurement between imperial and metric measurements.

A = a2
A = a × a

a = edge length

A = l × w

l = length
w = width

### Border Area Formula

A = (l1 × w1) – (l2 × l2)

l1 = outer length
w1 = outer width
l2 = inner length
w2 = inner width

A = 1/2(a + b)h

a = base a
b = base b
h = height

A = b × h

b = base
h = height

### Triangle Area Formula

s = 1/2(a + b + c)
A = s(s – a)(s – b)(s – c))

a = edge a
b = edge b
c = edge c

This formula is known as Heron’s formula. A simplified formula can also be used if the height of the triangle is known.

A = 1/2bh

b = edge b
h = height

### Circle Area Formula

A = πr2

If you know the diameter of the circle you can find the radius by dividing the diameter in half.

A = πab

a = axis a
b = axis b

A = (θ ÷ 360)πr2

θ = angle

### Regular Polygon Area Formula

A = (a2 × n) ÷ (4 × tan(π ÷ n))

a = edge length
n = number of sides

### Irregular Polygons and Complex Shapes

The trick to finding the area of an irregular polygon or complex shape is to break the shape up into regular polygons such as triangles and squares first, then find the area of those shapes and add them together to find the total.

Our surface area calculator can find the surface area of a 3-dimensional shape and our perimeter calculator can find the perimeter.