Square inches to square millimeters (in2 to mm2) area units conversion factor is 645.16. To find out how many square millimeters in square inches, multiply the square inch value by 645.16 or use the converter.
1 Square Inch = 645.16 Square Millimeters
There are 645.16 square millimeters in a square inch, because one inch is 25.4 millimeters and the area of a square is calculated by multiplying a side by itself, that makes 25.4 * 25.4 = 645.16 square millimeters in a square inch.
For example, to find out how many sq. millimeters there are in a sq. inch and a half, as a formula to convert from sq. inches to sq. millimeters, multiply the sq. inch value by 645.16, that makes 1.5 in2 * 645.16 = 967.74 sq. millimeters in 1.5 sq. inches.
Square inch is an imperial and US Customary area unit and defined as the area of a square with sides 1 inch in length. 1 square inch equals to 645.16 sq. millimeters and 6.45 sq. centimeters. The abbreviation is "in2".
Square millimeter is an area unit in metric system and defined as the area of a square with sides 1 millimeter in length. 1 square millimeter equals to 1/100 of a sq. centimeter. The abbreviation is "mm2".