It is a common misconception that 30 mm is bigger than 1. In actuality, 1 is bigger than 30 mm. This can be seen when comparing the two objects side by side. 1 is clearly larger than 30 mm. The reason that many people believe that 30 mm is bigger than 1 is because they are confusing the metric system with the imperial system. In the metric system, millimeters (mm) are smaller than centimeters (cm). However, in the imperial system, inches (in) are larger than feet (ft). Therefore, when people see the unit mm they think it must be referring to the metric system and assume that it is a small unit of measurement.