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:

Rectangle Area Calculator

Square Area Calculator

Border Area Calculator

Trapezoid Area Calculator

Parallelogram Area Calculator

Triangle Area Calculator

Circle Area Calculator

Ellipse Area Calculator

Sector Area Calculator

Regular Polygon Area Calculator

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.

Square Area Formula

A = a2
A = a × a

a = edge length

Calculate square area

Diagram of a square showing a = edge length

Rectangle Area Formula

A = l × w

l = length
w = width

Calculate rectangle area

Diagram of a rectangle showing l = length and w = width

Border Area Formula

A = (l1 × w1) – (l2 × l2)

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

Calculate border area

Diagram of a border showing l1 = outer length, w1 = outer width, l2 = inner length, and w2 = inner width

Trapezoid Area Formula

A = 1/2(a + b)h

a = base a
b = base b
h = height

Calculate trapezoid area

Diagram of a trapezoid showing a = base a, b = base b, and h = height

Parallelogram Area Formula

A = b × h

b = base
h = height

Calculate parallelogram area

Diagram of a parallelogram showing b = base and 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

Calculate triangle area

Diagram of a triangle showing a = edge a, b = edge b, and c = edge c

Circle Area Formula

A = πr2

r = radius

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

Calculate circle area

Diagram of a circle showing r = radius

Ellipse Area Formula

A = πab

a = axis a
b = axis b

Calculate ellipse area

Diagram of an ellipse showing a = axis a and b = axis b

Sector Area Formula

A = (θ ÷ 360)πr2

r = radius
θ = angle

Calculate sector area

Diagram of a sector showing r = radius and θ = angle

Regular Polygon Area Formula

A = (a2 × n) ÷ (4 × tan(π ÷ n))

a = edge length
n = number of sides

Calculate regular polygon area

Diagram of a regular polygon showing a = edge length

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.

Diagram of an irregular polygon/complex shape showing that it can be broken up into a triangle, rectangle, and square

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