Circle Length Calculator

If you want to learn how to calculate the length of a circle, our circle length calculator is the perfect tool 🎯. You can use this calculator to:

  • Find the length of the radius of the circle.
  • Calculate the length of the diameter of a circle.
  • Find the length of the circumference.

Read on to learn more about how to find the length of a circle.

Radius, diameter, and circumference: the circle length formula

Radius r, diameter d, and circumference c are related. The higher the radius or the diameter, the higher the circumference. The circle length formula connects these variables in a single equation:

c = 2πr

If you only know the diameter, you can find the length of the radius of the circle by simply remembering the diameter is twice the radius:

r = d/2

Reordering the equations, you can also calculate the length of the circle diameter in terms of the circumference:

d = c/π

Similarly, you can know what the length of the radius of the circle is:

r = c/(2π)

How to calculate the length of a circle?

Let’s suppose you want to know what is the length of the radius of a circle of 10 cm circumference. You can follow these steps:

  1. Use an adequate formula to solve your problem. In this case, it would be r = c/(2π).
  2. Input the circumference in the formula. The result should be: r = 10cm / (2π).
  3. Double-check your results. Input 10 cm in the circumference box of the circle length calculator. The result should also be 1.59155 cm for the radius.

Other awesome circle-related calculators

Now that you know how to find the length of a circle, you can look at these other great tools and keep improving your skills:

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


What is the length of half a circle?

The length of half a circle is π (pi) times radius, expressed with the formula as chalf = πr or chalf = πd/2. It is the length of an ordinary circle divided by two in this case.

What is the circumference of a 6-inch circle?

18.8496 inches. To find the circumference of any circle, multiply its diameter by π. In this instance:

  1. Take the circle’s diameter, which is 6 in.
  2. Multiply it by π.
  3. The result is 18.8496 in.

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