Square Inch to Circular Inch Converter
Unit Converter
Instant · Precise · Universal
23 units available
6 categories total
How to Convert Square Inch to Circular Inch
To convert in² to cm²: multiply by 6.4516. To ft²: divide by 144.
1 in² = 6.4516 cm² = 645.16 mm². There are 144 in² in 1 ft² and 1,296 in² in 1 yd².
For example, 1 Square Inch (in²) = 1.273239545 Circular Inch (circ in).
Square Inch to Circular Inch — Common Values
| Square Inch (in²) | Circular Inch (circ in) |
|---|---|
| 0.1 | 0.1273239545 |
| 0.5 | 0.6366197725 |
| 1 | 1.273239545 |
| 2 | 2.54647909 |
| 5 | 6.366197725 |
| 10 | 12.73239545 |
| 25 | 31.83098862 |
| 50 | 63.66197725 |
| 100 | 127.3239545 |
| 500 | 636.6197725 |
| 1000 | 1273.239545 |
About Square Inch (in²)
Definition
The square inch is an imperial unit of area equal to the area of a square with sides of exactly one inch (6.4516 cm²).
Mathematical Relationship
1 in² = 6.4516 cm² = 645.16 mm². There are 144 in² in 1 ft² and 1,296 in² in 1 yd².
Conversion Formula
To convert in² to cm²: multiply by 6.4516. To ft²: divide by 144.
Practical Applications
PSI (pounds per square inch) pressure measurement, print resolution, material cross-sections, and small parts dimensions.
Interesting Facts
The resolution of printed photos is measured in DPI (dots per inch). A 300 DPI print has 90,000 dots per square inch.
Common Mistakes
Thinking 1 ft² = 12 in² (it's actually 144 in², since 12 × 12 = 144). The square of the conversion factor catches people off guard.
Educational Tips
Remember: 1 ft = 12 in, so 1 ft² = 12² in² = 144 in². Always square the linear conversion factor.
About Circular Inch (circ in)
Definition
The circular inch is the area of a circle one inch in diameter, equal to π/4 square inches (approximately 0.0005067 m²).
Mathematical Relationship
1 circular inch = π/4 in² ≈ 0.7854 in² ≈ 5.067 cm². Equals 1,000,000 circular mils.
Conversion Formula
To convert circular inches to in²: multiply by 0.7854. To cm²: multiply by 5.067.
Practical Applications
Wire and cable cross-section calculations, especially for large conductors in power distribution.
Interesting Facts
The circular mil and circular inch exist solely to avoid π in cross-section math. Diameter² (in circular units) directly gives the area.
Common Mistakes
Confusing circular inch with square inch — a circular inch is about 78.5% of a square inch.
Educational Tips
For a circle: area in circular inches = diameter². Area in square inches = diameter² × π/4. The circular unit absorbs the π/4 factor.