Convert 1 square inch to square millimeter

1 in² (square inch) is equal to 645.16 mm² (square millimeter). To convert from square inch to square millimeter, multiply by 645.16 or divide by 0.0015500031000062.

• 1 in² × 645.16 = 645.16 mm²
• 1 in² ÷ 0.0015500031000062 = 645.16 mm²