Square Inches of a Circle Calculator

Square Inches of a Circle

Square inches of a circle is the area of a circle expressed in square inches (sq in or in²). This imperial unit is widely used in construction, carpeting, and manufacturing in the United States. Enter the radius or diameter in inches, feet, centimeters, or other units.

Formula

$$\text{Area (sq in)} = \pi r^2$$

Convert the radius to inches first, then apply the formula.

Worked Example

A circle with radius 3 cm equals $3 / 2.54 \approx 1.181$ inches. The area is $\pi \times 1.181^2 \approx 4.38$ sq in.

Frequently Asked Questions

How do I convert cm to square inches for a circle?

Convert the radius to inches (divide cm by 2.54), then compute $\pi r^2$.

How many square inches are in a square foot?

One square foot equals 144 square inches.

Can I use diameter instead of radius?

Yes. Select diameter mode and the calculator divides by 2 before computing the area.

Why use square inches instead of square feet?

Square inches give finer precision for smaller circular areas such as pipe cross-sections, gaskets, and small decorative items.

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Square Inches of a Circle Calculator