Quick answer: square inches = length (in) × width (in). 144 sq in = 1 sq ft; 1 sq in = 6.4516 cm². A 24 × 18 in panel is 432 sq in = 3 sq ft.
How to calculate square inches
- Measure the length and width in inches (or any unit; the calculator converts).
- Multiply length × width. The answer is in square inches.
- From feet: square feet × 144. From centimeters: cm² ÷ 6.4516.
Example: 60 × 45 cm = 2,700 cm², and 2,700 ÷ 6.4516 = 418.5 sq in.
Square inch conversions
| 1 square inch equals | Value |
|---|---|
| Square centimeters | 6.4516 (exact) |
| Square feet | 1 ÷ 144 = 0.006944 |
| Square yards | 1 ÷ 1,296 = 0.000772 |
The factors follow from the inch of 1959: 1 in = 2.54 cm exactly, as published by NIST.
Frequently asked questions
How do I calculate square inches?
Multiply the length by the width, both in inches. A panel 24 × 18 in is 432 square inches. If you measured in feet, multiply the square feet by 144.
How many square inches are in a square foot?
144, because a square foot is 12 in × 12 in. Divide square inches by 144 to get square feet: 432 sq in is 3 sq ft.
How do I convert square inches to square centimeters?
Multiply by 6.4516. The factor is exact, because an inch is exactly 2.54 cm and 2.54 × 2.54 = 6.4516.
How do I find the square inches of a circle?
Use π × radius². A 10 in pizza has a radius of 5 in, so its area is 3.1416 × 25 = 78.5 square inches. This calculator handles rectangles; for a circle use the formula.
Can I add several pieces together?
Yes. Use “+ Add another area” for each piece, or set “How many?” when several pieces are the same size.
Is this square inches calculator free to use online?
Yes. The CalcWall Square Inches Calculator is completely free and works online in any browser, on a phone, tablet or computer. There is nothing to download and no account to create, and the math runs right in your browser, so results appear as you type.