# Circle Perimeter Calculator

Our circle perimeter calculator can be of great help if you're struggling to solve geometry problems. One common problem is to find the **perimeter** of a circle, also called its **circumference**, which measures the length of the line forming this geometric figure. Keep reading if you want to know:

- What is the formula for circle perimeter.
- How to find the perimeter of a circle using the circle perimeter formula and our circle circumference calculator.
- What are the perimeters of a quarter circle and a half-circle.

🔎 Remember that, as with the rest of our tools, this circle circumference calculator works both ways - it is also a circumference to radius calculator - and you can use it to convert a circumference to a radius.

## The circle perimeter formula

If you don't know how to find the circumference of a circle, our calculator is the fastest option. Even so, it's **helpful to understand how equations work** to interpret the results better. The circle perimeter formula is:

`p = 2πr`

,

where `p`

is the circle's perimeter, `r`

is the radius, and `π`

is a constant equal to approximately 3.14159265...

You can also express the perimeter in terms of the diameter (`d`

), remembering that `r=d/2`

:

`p = πd`

💡 The number **π** is a constant equal to the **ratio of the circumference to the diameter** (or twice the radius). It'll always have the same value, independently of the size of the circle.

Solving for `π`

in the above equation results in the mentioned ratio: `π = p/(2r)`

.

### Half circle and quarter circle perimeter formulas

Sometimes we need to calculate portions of a circle instead of a whole one. We can obtain the formulas for the perimeters of a **half-circle** and a **quarter-circle** by dividing the above equation by 2 and 4, respectively:

p_{half} = πr

p_{quarter} = πr/2

## How to calculate the perimeter of a circle?

If you want to use the circle perimeter calculator to find the circumference of a circle, follow these steps:

**Determine the radius**of your circle. For example, let's suppose it's 7 cm.**Input the radius**in the calculator, and you'll know the circle's circumference. The result should be 43.982 cm.- To
**double-check your result**, enter the radius in the circle perimeter formula:`p = 2 × π × (7 cm) = 43.982 cm`

.

## Other helpful tools beyond the circle perimeter calculator

Now that you know how to find the perimeter of a circle don't forget that the circumference to radius calculator is not our only tool dealing with circular objects. We're hopeful that the calculators below will help you with your day-to-day circular problems:

- Circle calc: find c, d, a, r;
- Circle measurements calculator;
- Circle formula calculator;
- Radius of a circle calculator;
- Circle length calculator;
- Circumference to diameter;
- Diameter of a circle calculator;
- Circumference and area of a circle calculator;
- Square footage of a circle calculator; and
- Square inches of a circle calculator.

## FAQ

### How do I find the perimeter of a quarter circle?

To find the perimeter of a quarter circle:

- Remember the perimeter of an ordinary circle, which is
`p = 2πr`

. - Divide it by four, as you only want the perimeter of a quarter circle.
- The result should be
`p = πr/2`

. That is the perimeter of a quarter circle for any radius.

### How do I find the perimeter of a half-circle?

Multiply the radius by π (pi), and you'll get the half-circle perimeter. The perimeter of a half-circle is simply the perimeter of an ordinary circle divided by two, which results in `p = πr`

.

### What is the perimeter of a 10-inch circle?

31.416 inches. To find the **perimeter** of any circle, multiply the **diameter** by the number pi (π). In this case, 10 in × π = 31.416 in.