Ring Square Footage Calculator

When you first hear the phrase ring square footage, it might sound contradictory—aren’t rings circular? How can they have square footage? It’s a fair question, and you're not the only one wondering. But whether you’re designing a round patio, planning a circular garden, or working on a decorative element like a donut-shaped rug, understanding how to measure the square footage of a ring-shaped area can come in handy more often than you think.

What Is Ring Square Footage?

Let’s start with the basics. Ring square footage refers to the area found between two concentric circles—think of it like the “dough” of a donut. You’re not measuring the hole in the middle, nor the entire space including the center, but just the ring-shaped band itself.

Unlike square or rectangular spaces where you calculate area by multiplying length by width, a ring involves circles—so you’ll need a different approach. Specifically, you calculate the area of the larger circle and subtract the area of the smaller, inner circle to find just the ring portion.

Try out Sector Square Footage Calculator

Ring Square Footage Formula

Okay, so now that you know what ring square footage actually means, let’s talk about how to calculate it. Don’t worry — it’s easier than you might think, and you don’t need to dust off your high school geometry textbook to follow along.

When you’re measuring the area of a ring-shaped space, you’re essentially finding the difference between the area of two circles:

• The outer circle (the whole shape, including the center), and

• The inner circle (the empty space or hole in the middle)

The formula looks like this: Area of a ring = π × (R² - r²)

Where:

• π (pi) ≈ 3.1416

• R is the outer radius (from the center to the outer edge)

• r is the inner radius (from the center to the inner edge)

Example:

Suppose you’re measuring a circular garden with a small pond in the center:

• Outer radius: 20 feet

• Inner radius: 8 feet

1. Square both radii:
   20² = 400
   8² = 64

2. Subtract:
   400 − 64 = 336

3. Multiply by π:
   336 × 3.1416 ≈ 1,055.57 square feet

So, the square footage of the ring-shaped garden area would be about 1,055.57 square feet

Radius vs. Diameter: Don’t Mix Them Up

Here’s where many people slip:
Radius is the distance from the center to the edge.
Diameter goes all the way across through the center.

So if you're given a diameter, divide by 2 before using the formula.

Example:
Diameter = 40 feet → Radius = 20 feet

How to Calculate a Boxing Ring’s Square Footage

To really make this clear, let’s walk through a practical example you might encounter. Now, a fun fact for you: while we often call it a “boxing ring,” most boxing rings today are actually square. But in some traditional martial arts settings or custom events, circular rings are still used — and that's where knowing how to calculate ring square footage matters.

You’re asked to help set up a circular boxing ring for a local exhibition match. The event organizers have designed a ring with:

• An outer diameter of 30 feet

• An inner open space (center platform or no-contact zone) with a diameter of 10 feet

How much flooring material will you need to cover just the ring area, excluding the central no-contact space?

Step 1: Convert Diameters to Radii

Since the formula uses radii, you need to divide both diameters by 2.

• Outer radius (R) = 30 ÷ 2 = 15 feet

• Inner radius (r) = 10 ÷ 2 = 5 feet

Step 2: Square Both Radii

Now, square both values.

• 15² = 225

• 5² = 25

Step 3: Subtract the Inner Area from the Outer Area

Subtract the area of the inner circle from the outer circle.

225 - 25 = 200

Step 4: Multiply by Pi (3.1416)

Now, multiply the result by 3.1416.

200 × 3.1416 = 628.32

Final Result: The total ring square footage you’ll need to cover with flooring material is 628.32 square feet.

Try out Annulus Area Calculator

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