Square Inch Calculator
Enter length and width. A US Letter sheet, 8.5 by 11 inches, is 93.5 square inches.
Sources: NIST SP 811, NIST Handbook 44 Updated
Result
8.5 × 11 in = 93.5 in²
= 0.649306 ft²
= 603.225 cm²
The formula
square inches = length × width (both in inches)
For sides given in feet or centimeters the calculator works out the area in that unit and converts it exactly: 1 ft² = 144 in² and 1 in² = 6.4516 cm².
Worked example: a US Letter sheet
- Multiply length by width: 8.5 × 11 = 93.5 square inches.
- In square feet: 93.5 ÷ 144 = 0.6493 ft².
- In square centimeters: 93.5 × 6.4516 = 603.22 cm².
Reference sizes
| Size | Square inches | Square feet |
|---|---|---|
| 3 in × 5 in | 15 | 0.104 |
| 4 in × 6 in | 24 | 0.167 |
| 8.5 in × 11 in | 93.5 | 0.649 |
| 12 in × 12 in | 144 | 1 |
| 18 in × 24 in | 432 | 3 |
| 24 in × 36 in | 864 | 6 |
| 48 in × 96 in | 4,608 | 32 |
12 in × 12 in is exactly one square foot, and a 4 ft × 8 ft sheet (48 in × 96 in) is exactly 32 square feet.
Frequently asked questions
How do I calculate square inches?
Multiply the length by the width, both in inches. A sheet 8.5 in by 11 in is 8.5 × 11 = 93.5 square inches.
How many square inches are in a square foot?
144, because a square foot is 12 inches by 12 inches. To turn square inches into square feet, divide by 144.
How many square centimeters is a square inch?
Exactly 6.4516, which is 2.54 × 2.54.
Can I enter fractions?
Yes. Type 3 5/8 or 5/16 as well as decimals. Fractions are read exactly.
What about a circle or a triangle?
Length × width only works for rectangles. A circle is π × radius² and a triangle is half of base × height.
Sources
- NIST Special Publication 811, Appendix B.8 — 1 square inch = 6.4516 cm² exactly (checked October 12, 2026)
- NIST Handbook 44 (2026), Appendix C — 144 square inches = 1 square foot (checked October 12, 2026)