Circumference to Diameter Calculator

Created by Luis Fernando
Reviewed by Wojciech Sas, PhD candidate
Last updated: Mar 15, 2022

The circumference to diameter calculator can help you solve the geometry problem of finding the circumference of a circle by inputting its diameter.

This calculator works both ways, so you can also convert circumference to diameter.

Keep reading to learn more about:

  • The circumference to diameter formula.
  • How to calculate circumference from the diameter.
  • How to get diameter from the circumference.

The circumference to diameter formula

Diameter and circumference are lengths related to each other — the higher the diameter, the higher the circumference. The circumference to diameter formula connects these variables in a single equation:

c = πd,


  • c stands for the circumference;
  • d for the diameter; and
  • π is the pi number.

If, on the other side, you're interested in how to calculate diameter from the circumference, you can solve for d in the above equation:

d = c/π.

💡 Did you know?
As you can imagine from the above equations, the number π is a constant equal to the circumference-to-diameter ratio of a circle (π=c/d). If you divide the circumference of a circle by its diameter, independently of the size, it'll always be 3.14159265...

How to find circumference from diameter: an example

Let's look at an example. Suppose you want to find the circumference of a 5 cm diameter circle. These would be the steps to follow:

  1. Use the appropriate equation, which, in this case, is the circumference to diameter formula: c = πd.
  2. Input the diameter in the equation: c = π × (5 cm) = 15.708 cm.
  3. That's it. Also, check your results using our circumference to diameter calculator. Input 5 cm in the diameter box. Your result should also be 15.708 cm.


What is the circumference of a 6-foot diameter circle?

18.8496 feet. To convert diameter to circumference:

  1. Take the diameter.
  2. Multiply it by the number pi (π).
  3. In this case, the circumference equals: π × 6 ft = 18.8496 ft.

How do I get diameter from circumference?

Divide the circumference value by the number pi (π), or use the formula d = c/π. That's how you find the circumference of a circle with its diameter.

Luis Fernando
Image of a circle with radius, diameter, circumference and area marked.
Diameter (d)
Circumference (c)
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