Circle Area Calculator

Calculate the area of a circle from radius, diameter, circumference, or known area. Estimate square feet, square inches, square yards, square meters, radius, diameter, circumference, waste, material quantity, and project cost.

Calculate Circle Area

Circle Area = π × Radius². Diameter = 2 × Radius. Circumference = 2 × π × Radius.
Your result will appear here.

How the circle area calculator works

Radius mode:
The calculator squares the radius and multiplies it by pi to estimate circle area.

Diameter mode:
The calculator divides the diameter by 2 to find the radius, then calculates the area.

Circumference mode:
The calculator uses the circumference to estimate radius, diameter, and area.

Known area mode:
The calculator converts a known area and estimates the circle radius, diameter, and circumference from it.

Why use a circle area calculator?

A circle area calculator helps estimate round spaces for patios, pools, garden beds, fire pits, concrete pads, lawns, tables, pavers, landscaping, and construction planning.

It can help calculate square footage, compare area units, estimate material quantity, add extra waste, and estimate project cost.

What your result means

Your result shows the circle area, radius, diameter, circumference, area with extra waste, estimated pieces or units needed, and estimated cost based on the values you enter.

Circle area formulas

Frequently asked questions

How do I calculate the area of a circle?

Square the radius, then multiply by pi. For example, a circle with a 6 foot radius has an area of about 113.10 square feet.

What is the formula for circle area?

The formula is Area = π × Radius².

How do I calculate circle area from diameter?

Divide the diameter by 2 to get the radius. Then square the radius and multiply by pi.

How do I calculate circle area from circumference?

Divide the circumference by 2π to find the radius. Then use Area = π × Radius².

Should I add waste for circular materials?

Yes. Round layouts often create cuts and offcuts. For pavers, sod, landscaping fabric, tile, concrete, mulch fabric, or flooring, adding 5% to 15% extra is commonly helpful.