How to convert square Inches to square millimeters

1 square Inches (in^2) is equal to 645.160624 square millimeters (mm^2). Conversely, 1 square millimeters (mm^2) is equal to 1.5500016×10^-3 square Inches (in^2).

Step by step guide to convert square inches to square millimeters

Converting units

Millimetre is a SI unit and inches is an Imperial and American customary unit. For this conversion, we use metric prefix to help us understand milli prefix. Square millimeter or mm^2 is an area which is 1mm long and 1mm wide. There is 0.039370 inches in a millimeter or 1 inch is officially defined as 25.4 millimetres. Thus,

$$0.039370\ in * 0.039370\ in = 1\ mm * 1\ mm$$

$$0.0015499969\ in^{2} = 1\ mm^2$$

or

$$1\ in^{2} = 645.16062\ mm^2$$

Wikipedia page for Millimetre
Wikipedia page for Inch