To convert square inches to square millimeters, multiply the value by 645.16. To go the other way, multiply square millimeters by 0.00155 to get square inches.
| Square Inches (in²) | Square Millimeters (mm²) |
|---|---|
| 1 in² | 645.16 mm² |
| 2 in² | 1,290.32 mm² |
| 5 in² | 3,225.8 mm² |
| 10 in² | 6,451.6 mm² |
| 20 in² | 12,903.2 mm² |
| 50 in² | 32,258 mm² |
| 100 in² | 64,516 mm² |
| 500 in² | 322,580 mm² |
| 1,000 in² | 645,160 mm² |
Square inch (in²). A square inch is the area of a square with 1-inch sides (6.4516 cm²).
Square millimeter (mm²). A square millimeter is the area of a square with 1 mm sides, used for small parts, wire and pipe cross-sections.
There are 645.16 square millimeters in one square inch.
Multiply the number of square inches by 645.16. For example, 10 square inches equal 6,451.6 square millimeters.
One square millimeter equals 0.00155 square inches.