Convert Square Inches to Square Millimeters
Convert Square Inches (in²) to Square Millimeters (mm²) instantly and accurately.
Conversion Formula
mm² = in² × 645.16
About Square Inches
A square inch (in²) is an imperial unit of area equal to a square with sides of one inch (25.4 mm × 25.4 mm). It is commonly used in the United States for measuring small areas like fabric swatches, screen sizes, or printed materials. A standard business card is about 6 in², and a typical smartphone screen might be 15-20 in². This unit remains prevalent in American manufacturing, printing, and retail.
About Square Millimeters
A square millimeter (mm²) is a metric unit of area equal to a square with sides of one millimeter. It is commonly used in precision engineering, electronics, and measuring very small surfaces such as microchips or printed circuit boards. To visualise: a typical pinhead has an area of about 2-3 mm². This unit is essential in microscopy, medical imaging, and manufacturing where tiny, precise measurements are critical.
Quick Reference Table
| Square Inches (in²) | Square Millimeters (mm²) |
|---|---|
| 1 in² | 645.16 mm² |
| 2 in² | 1290.32 mm² |
| 5 in² | 3225.8 mm² |
| 10 in² | 6451.6 mm² |
| 25 in² | 16129 mm² |
| 50 in² | 32258 mm² |
| 100 in² | 64516 mm² |