How to Calculate the Circumference of a Circle

Circles are all around us—wheels, plates, clocks, coins. But have you ever wondered how to figure out the distance around a circle? That’s called the circumference.

In this article, we’ll explain what circumference means, give you the exact formula, show you how to calculate it step by step, and include a handy calculator and infographic to make it even easier.

✨ Enter the radius or diameter and the tool will calculate the circumference of the circle

🌀 What Is Circumference?

The circumference is just a fancy word for the perimeter of a circle—in other words, how far it is around the edge.

If you could “unwrap” a circle and lay it out flat like a straight line, the length of that line would be the circumference.

🧾 Circumference Formula

There are two main formulas, depending on what you know:

If you know the radius:

Circumference = 2 × π × r

Where r is the radius (half the diameter)

If you know the diameter:

Circumference = π × d

Where d is the diameter (the full width across the circle)

Use π (pi) ≈ 3.1416 unless your calculator has a π button

📊 Example 1: Using Radius

Let’s say your circle has a radius of 7 cm:

Circumference = 2 × π × 7 = 2 × 3.1416 × 7 ≈ 43.98 cm

📏 Example 2: Using Diameter

If the diameter is 10 cm:

Circumference = π × 10 ≈ 31.42 cm

✅ Simple, right?

🔢 Circumference Calculator

Want to skip the math? Use the calculator on this page.

🎯 Real-Life Uses

• Finding out how far a wheel rolls in one rotation
• Calculating distance around circular tracks or round tables
• Estimating border length for circular gardens or fountains

🧠 Final Thoughts

Now you know how to find the distance around any circle! Whether you’re a student, DIYer, or just curious, remembering these simple formulas will make your life easier every time a circle comes into play.