Area Calculator – Calculate Area of Various Shapes

Calculate area by selecting a shape and entering your measurements in any metric or US customary unit. See the formulas to calculate the area for each shape below.

Select a Shape:

Rectangle

Square

Border

Trapezoid

Parallelogram

Triangle

Circle

Ellipse

Sector

Regular Polygon



How to Calculate Area

Area is the space inside the perimeter/boundary of space, and its symbol is (A). It’s the size of a 2-dimensional surface and is measured in square units, for example, square feet.

Square feet can also be expressed as ft2 or sq. ft. Use our formulas to find the area of many shapes.

It’s essential to measure all lengths in the same unit of measure or convert all lengths to the same unit before calculating area. Try our length unit conversion calculators or area unit conversion calculators for converting between imperial and metric measurements.

Use the formulas below to calculate the area of many popular shapes.


Square Area Formula

A = a2
A = a × a

a = edge length

Diagram of a square showing a = edge length

Rectangle Area Formula

A = l × w

l = length
w = width

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

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

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

Parallelogram Area Formula

A = b × h

b = base
h = height

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. You can also use a simplified formula if the height of the triangle is known.

A = 1/2bh

b = edge b
h = height

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 circle’s diameter you can find the radius by dividing the diameter in half.

Diagram of a circle showing r = radius

Ellipse Area Formula

A = πab

a = axis a
b = axis b

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

Sector Area Formula

A = (θ ÷ 360)πr2

r = radius
θ = angle

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

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

Difference Between Area and Surface Area

You might be wondering how area is different from surface area. While area is the size of a two-dimensional plane, surface area is the size of the surface of a three-dimensional solid shape.

Difference Between Area and Perimeter

So what is the difference between perimeter and area? Perimeter is the distance around a two-dimensional shape, while area is the size of the shape itself.

Of course, we have a perimeter calculator to help solve this length measurement.