Circumference of a Circle Calculator

This Circumference of a Circle Calculator helps you find the distance around a circle when the radius is known. It uses the formula C = 2πr, where r is the radius and the answer is written in units. Multiply the radius by 2π to get the circumference. It is a simple way to check answers, understand the circle circumference formula, and practise basic geometry step by step.

In the diagram, the radius is labeled r.

Step-by-step method

1. Identify what is given.
2. Write the formula.
3. Substitute the value and calculate the circumference.

Formula:

Example 1:

Step 1 - Identify what is given.

In this problem: The given radius is \(r = 5\).

Step 2 - Write the formula.

In this problem: Use the circumference formula: \(C = 2\pi r\).

Step 3 - Substitute the value and calculate the circumference.

In this problem: Substitute \(r = 5\): \(C = 2 \times \pi \times 5 \approx 31.42\).

Final answer:

Example 2:

Step 1 - Identify what is given.

In this problem: The given radius is \(r = 3.5\).

Step 2 - Write the formula.

In this problem: Use the circumference formula: \(C = 2\pi r\).

Step 3 - Substitute the value and calculate the circumference.

In this problem: Substitute \(r = 3.5\): \(C = 2 \times \pi \times 3.5 \approx 21.99\).

Final answer: