What is the size of a roundworm in inches?

Roundworms, specifically the species Caenorhabditis elegans, typically measure about 0.04 inches (1 millimeter) in length. However, other roundworm species can vary significantly in size, ranging from a few millimeters to over 12 inches (30 centimeters) in some parasitic varieties. Generally, most roundworms fall within the range of 0.04 to 12 inches depending on the species.