# Perimeter Calculator

Calculate the perimeter of a shape by selecting a shape and entering your measurements in any unit, metric or imperial. We’ve included the formulas for each shape below.

## Perimeter Result:

## On this page:

- Perimeter Calculator
- How to Find the Perimeter of a Shape
- Perimeter Formulas
- Square Perimeter Formula
- Rectangle Perimeter Formula
- Trapezoid Perimeter Formula
- Parallelogram Perimeter Formula
- Rhombus Perimeter Formula
- Triangle Perimeter Formula
- Circle Perimeter Formula
- Ellipse Perimeter Formula
- Sector Perimeter Formula
- Sector Perimeter Formula
- Pentagon Perimeter Formula
- Hexagon Perimeter Formula
- Octagon Perimeter Formula
- Regular Polygon Perimeter Formula

## How to Find the Perimeter of a Shape

Perimeter is the length of the outer edge or boundary of a two-dimensional shape and is expressed in units of length, such as inches or feet. The word *perimeter* is actually derived from the Greek words peri (‘around’) and metron (‘measure’), meaning a measurement around something.

Since perimeter is the total boundary length, it is equal to the sum of the edge lengths for polygons with multiple edges.

So, you can find the perimeter of any polygon by measuring each edge of the shape and adding the edge lengths together to get the total length. For instance, for a rectangle, the perimeter is equal to the length plus the length plus the width plus the width.

For shapes with curved edges, such as a circle or ellipse, the perimeter is referred to as the circumference, and you’ll need a formula to find it.

When measuring, use the same unit of measurement for each edge, and use our length converter to convert all measurements to the same length if needed.

### Perimeter Formulas

Each shape has a unique formula for its perimeter; see the formulas for the most common shapes below.

#### Square Perimeter Formula

P = 4a

a = edge length

#### Rectangle Perimeter Formula

P = 2l + 2w

l = length

w = width

#### Trapezoid Perimeter Formula

P = a + b + c + d

a = base a

b = base b

c = side c

d = side d

#### Parallelogram Perimeter Formula

P = 2a + 2b

a = side

b = base

#### Rhombus Perimeter Formula

P = 4a

a = edge length

#### Triangle Perimeter Formula

P = a + b + c

a = edge a

b = edge b

c = edge c

#### Circle Perimeter Formula

P = 2πr

r = radius

Try our circumference calculator to solve using the radius, diameter, or area.

#### Ellipse Perimeter Formula

P ≈ π[3(a + b) – (((3a + b))(a + 3b))]

a = axis a

b = axis b

#### Sector Perimeter Formula

P = 2r + ((2θπr) ÷ 360)

r = radius

θ = angle in degrees

#### Sector Perimeter Formula

P = πrθ / 180 + 2r × sin(θ / 2)

r = radius

θ = angle in degrees

#### Pentagon Perimeter Formula

P = 5a

a = edge length

#### Hexagon Perimeter Formula

P = 6a

a = edge length

#### Octagon Perimeter Formula

P = 8a

a = edge length

#### Regular Polygon Perimeter Formula

P = an

a = edge length

n = number of sides

To find the area of these shapes, try our area calculator.