You can convert millimeters to meters squared if you have the measurements of an area in millimeters. Millimeters and meters squared are both units that are used in the metric system of measurement. One thousand millimeters are equivalent to one meter. Because millimeters are a measure of distance, and meters squared are a measure of area, you must have the measurements of the length and width of an area to convert millimeters to meters squared.
Measure the length of the area in millimeters. For example, say you have a rectangle that is 450 millimeters long. Record this value.
Measure the width of the area in millimeters. For example, say the rectangle is 300 millimeters wide. Record this value.
Multiply Length and Width
Multiply the measurements from Step 1 and Step 2 together to find the area, because area = length x width. In this case, work out 450 x 300 = 135,000. Record the result.
Divide by 1000
Divide the result from Step 3 by 1,000, because one meter squared is equal to 1,000 millimeters. Work out 135,000 ÷ 1,000 = 135. The rectangle is 135 meters squared.