# Circumference and Area of a Circle Calculator

Are you interested in calculating the area and circumference of a circle and the formula behind it? This is the perfect tool.

**Circles are present in many places**. Coins, pizzas, and vinyl disks are examples of circular objects, and the area is an essential aspect of them.

Read on if you're interested in:

- How to find the area and circumference of a circle.
- How the circumference and area of a circle relate to each other.
- How to find the area of a quarter circle.

💡 **Did you know**

The diameter and, therefore, the area of a pizza are critical in determining the optimum pizza size for your budget and taste. In fact, we have a pizza cost comparison calculator for your delight.

## Formula to calculate the circumference and area of a circle

These are the formulas to calculate the circumference and area of a circle:

`c = 2πr`

`A = πr² = πd²/4`

, where:

`c`

stands for circumference;`r`

for radius; and`d`

for the diameter of the circle.

`π`

is a constant approximately equal to 3.14159265359 and, among other things, represents the circumference-to-diameter ratio of **any circle**.

## How to find the circumference and area of a circle?

Suppose you want to know how to find the **circumference and area of a circle with an 8 cm radius**. In that case, these would be the steps to follow:

**Use the formulas**to calculate the circumference and area:`c = 2πr`

and`A = πr²`

.- The
**circumference**should equal`c = 2π × 8 cm = 50.265 cm`

. - The
**area**should equal`A = π × (8 cm)² = 201.06 cm²`

. - To
**check your results**, input the 8 cm diameter in the calculator. The results should also be 50.265 cm and 201.06 cm².

## Other awesome Omni Calculators

After mastering the process of calculating the circumference of and area of circles, you may look at these other tools and keep improving your skills:

- 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;
- Circle perimeter calculator;
- Square footage of a circle calculator; and
- Square inches of a circle calculator.

## FAQ

### How are the circumference and area of a circle related?

They relate to each other by the following formula: `c = 2√(πA)`

. The equation says **circumference is proportional to the square root of the area**, so the bigger the circle size, the greater the circumference.

### What is the area of a 9-inch circle?

**63.617 in²**. To find the area of any circle, given its diameter:

- Multiply π (pi) by the diameter square:
`π × (9 in)² = 254.47 in²`

. - Divide that result by four:

`254.47 in²/4 = 63.617 in²`

. - Now you know what the area of a 9-inch circle is ✔️

### How do I find the area of a quarter-circle?

To get the area of a quarter-circle:

- Take the formula of the area of an ordinary circle:
`A = πr²`

. - Divide that formula by four.
- After following these steps, we can note that
**the area of a quarter circle is**.`A = πr²/4`