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.

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.

1. The first one is based on the radius of the circle. The diameter equals the length of two radiuses.

   $d=2r$

2. Area of a circle:

   $d=2\sqrt{\frac{a}{π}}$

3. Circumference of a circle:

   $d=\frac{c}{π}$

where:

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

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

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 the diameter and r is the radius.

The diameter is the radius multiplied by two. How to calculate the radius? Measure the distance from the center to any point on the 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 its diameter is 6.37 in.