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Circumference to Diameter Calculator

Created by Luis Hoyos
Reviewed by Wojciech Sas, PhD
Last updated: Jan 18, 2024

The circumference to diameter calculator can help you solve the geometry problem of finding the diameter of a circle by inputting its circumference. This calculator works both ways, so you can also convert a diameter to a circumference.

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:

d = c/π


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

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

c = π × d

💡 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 by the 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 diameter of a circle with its circumference.

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