Circle Square Foot Calculator — Radius & Diameter

Q: How do I calculate the square footage of a circle?

Use the formula Area = pi x (Diameter / 2) squared. A circle with a 12-foot diameter has an area of 113.10 square feet.

Q: What is the formula for circle area?

Area = pi x r squared, where r is the radius (half the diameter). Pi equals approximately 3.14159.

Q: How many square feet is a 10-foot diameter circle?

A 10-foot diameter circle is 78.54 square feet (pi x 5 squared = 78.54 sq ft).

Q: How do I find the radius of a circle?

Divide the diameter by 2. The diameter is the full width of the circle through the center. A 20-foot diameter circle has a 10-foot radius.

Q: Can I use this for circular patios?

Yes, enter the patio diameter to calculate its area. Add a material price per square foot to estimate paving or concrete costs.

What is circle square footage?

Circle square footage equals pi times radius squared. Multiply π × r² in feet (π = 3.14159). A circle with a 10 ft (3.05 m) radius has 314.16 sq ft (29.19 m²). For a pie-slice section of a circle, use the sector calculator.

Getting started

How to Calculate Circle Square Footage

To calculate circle square footage, measure the radius (center to edge) or diameter (across) in feet. Apply Area = π × r². If you have diameter, divide by 2 first to get radius.

1. Measure radius or diameter

Measure from circle center to edge (radius) or across the full circle (diameter). Diameter = 2 × radius.

2. Apply π × r²

Circle area = π × radius². A 10 ft radius circle has 314.16 sq ft.

3. Use for round shapes

Apply circle area to round patios, fire pit zones, swimming pools, and circular gardens.

Quick reference

Reference

1 acre = 43,560 square feet

1 square yard = 9 square feet

1 square meter = 10.764 square feet

1 square inch = 0.00064516 square feet

Material pricing

Calculate Cost of Materials

Circle area times price per unit equals material cost. Multiply circle square footage by price for pavers, concrete, sod, or mulch.

There are 2 steps to calculate material cost:

Enter the price per square foot of pavers, concrete, sod, or mulch covering the circle.
The Square Foot Calculator multiplies circle area by the unit price for material total.

Round shapes need 10-15% extra material for curved-edge cuts. Order extra pavers, sod, or concrete to avoid running short.

FAQ

Frequently Asked Questions

How do I calculate the square footage of a circle?

Use the formula Area = pi x (Diameter / 2) squared. A circle with a 12-foot diameter has an area of 113.10 square feet.

What is the formula for circle area?

Area = pi x r squared, where r is the radius (half the diameter). Pi equals approximately 3.14159.

How many square feet is a 10-foot diameter circle?

A 10-foot diameter circle is 78.54 square feet (pi x 5 squared = 78.54 sq ft).

How do I find the radius of a circle?

Divide the diameter by 2. The diameter is the full width of the circle through the center. A 20-foot diameter circle has a 10-foot radius.

Can I use this for circular patios?

Yes, enter the patio diameter to calculate its area. Add a material price per square foot to estimate paving or concrete costs.

How much concrete do I need for a circular pad?

Calculate the circle area in square feet, then multiply by the depth in feet to get cubic feet. Divide by 27 to convert to cubic yards for ordering concrete.

REFERENCES

Circle Square Foot
Calculator — Radius & Diameter

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