# 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

## On this page:

- Area Calculator - Find Area
- How to Find Area
- Square Area Formula
- Rectangle Area Formula
- Border Area Formula
- Trapezoid Area Formula
- Parallelogram Area Formula
- Triangle Area Formula
- Circle Area Formula
- Ellipse Area Formula
- Sector Area Formula
- Regular Polygon Area Formula
- Irregular Polygons and Complex Shapes

## 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 ft^{2}. 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.

### Border Area Formula

A = (l1 × w1) – (l2 × l2)

l1 = outer length

w1 = outer width

l2 = inner length

w2 = inner width

### Trapezoid Area Formula

A = ^{1}/_{2}(a + b)h

a = base a

b = base b

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}/_{2}bh

b = edge b

h = height

### Circle Area Formula

A = πr^{2}

r = radius

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

### Regular Polygon Area Formula

A = (a^{2} × 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.