Square Inches Calculator
Calculate area in square inches for rectangles, circles, and triangles. Enter in inches, cm, mm, or feet. Convert to sq ft, cm², mm², and m².
📐 Square Inches Calculator
IMPERIAL
METRIC
💡 How to Calculate Square Inches
Square inches (sq in or in²) measure small areas in the US customary system. They're used for tiles, screens, paper, fabric swatches, gaskets, pipe cross-sections, and craft projects. For larger areas, use our square footage calculator or square yards calculator.
The calculator above supports 3 shapes (rectangle, circle, triangle), accepts 4 input units (inches, cm, mm, feet), and converts to both imperial and metric area units. Pair it with our inch fraction calculator for tape-measure conversions.
Square Inches Formulas
| Shape | Formula | Example |
|---|---|---|
| Rectangle | L × W | 12 × 8 = 96 sq in |
| Circle | π × r² | r = 6" → π × 36 = 113.1 sq in |
| Triangle | ½ × base × height | 10 × 8 ÷ 2 = 40 sq in |
All dimensions must be in inches. The calculator converts from cm, mm, or feet automatically.
Square Inches to Square Feet
Square feet = square inches ÷ 144
Since 1 foot = 12 inches, 1 sq ft = 12 × 12 = 144 sq in.
Quick conversions:
- 72 sq in = 0.5 sq ft
- 144 sq in = 1 sq ft
- 288 sq in = 2 sq ft
- 432 sq in = 3 sq ft
- 1,008 sq in = 7 sq ft
Common Object Sizes in Square Inches
| Object | Dimensions | Square Inches | Square Feet |
|---|---|---|---|
| Credit card | 3.37 × 2.13" | 7.2 | 0.05 |
| Index card | 3 × 5" | 15 | 0.10 |
| Letter paper | 8.5 × 11" | 93.5 | 0.65 |
| Legal paper | 8.5 × 14" | 119 | 0.83 |
| 12 × 12" tile | 12 × 12" | 144 | 1.00 |
| Pizza (14" dia) | r = 7" | 154 | 1.07 |
| Poster (18 × 24") | 18 × 24" | 432 | 3.00 |
Screen Sizes in Square Inches
| Screen | Diagonal | Approx Area (sq in) |
|---|---|---|
| iPhone 15 | 6.1" | ~16 |
| iPad (10.9") | 10.9" | ~64 |
| Laptop (15.6") | 15.6" | ~92 |
| Monitor (24") | 24" | ~219 |
| Monitor (27") | 27" | ~277 |
| TV (55") | 55" | ~1,150 |
| TV (65") | 65" | ~1,606 |
Area Conversion Reference
| Unit | To sq in | To sq ft | To cm² |
|---|---|---|---|
| 1 sq in | 1 | 0.00694 | 6.4516 |
| 1 sq ft | 144 | 1 | 929.03 |
| 1 cm² | 0.155 | 0.00108 | 1 |
| 1 mm² | 0.00155 | 0.0000108 | 0.01 |
| 1 m² | 1,550 | 10.764 | 10,000 |