# Diameter of a Circle Calculator

If you're wondering how to calculate the diameter of a circle, this diameter of a circle calculator is a perfect choice.

You will need either the **radius**, **the circumference**, or **the area** of a given circle for the calculations. Take a look at the picture above the calculator to visualize each element.

## How do I calculate the diameter of a circle?

There are three methods for diameter estimation. Choose the useful one based on the data you have. This calculator will automatically estimate all of the other values.

**The first one bases on the radius of the circle.**The diameter equals the length of two radiuses.

$d=2r$

**Area of a circle**:

$d=2\sqrt{\frac{a}{π}}$

**Circumference of a circle**:

$d=\frac{c}{π}$

Where:

**r**stands for radius of the circle,**c**for circumference,**A**for area, and**d**stand for diameter of the circle.

## Other circle calculators

If you were looking for the diameter of a circle calculator, here are a couple more tools that may interest you:

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

## FAQ

### What is the diameter of a 9 inch circle?

If the circle radius is 9 inches, then the **diameter is 18 inches**. The easiest formula for the diameter is $d=2r$, where d is diameter and r radius.

### How to measure the diameter of a circle?

**The diameter is the radius multiplied by two**. How to calculate radius? Measure the distance from the center to any point on the circle.

### How do you find the radius and diameter of a circle?

To calculate the radius of a circle, divide its circumference by 2π; **for the circle's diameter, divide the circumference by π**.

Let's say that the circumference of a given circle is 20 inches. Therefore, its radius is 3.18 in and diameter 6.37 in.