A length of 15 millimeters is the same as a length of 0.59 inches. To convert millimeters into inches, divide the number of millimeters by 25.4 inches per millimeter. An example of an organism that is about 15 millimeters long is a cockroach.
The conversion between millimeters and inches is often seen in the jewelry business and as a distinction between standard and metric tools. Metric measurements, such as the millimeter and meter, are used as the standard for measuring length in most countries. The United States is an exception to this, as it uses inches and feet to measure length.