An inch equals:

An inch is defined as exactly 2.54 centimeters. This conversion is widely accepted and utilized in various fields, including engineering, manufacturing, and healthcare, particularly in pedorthics, where precise measurements of footwear and orthotic devices are crucial. The definition provides a clear understanding of the relationship between the imperial and metric systems, allowing for accurate conversions between these units of measure. Understanding this conversion is important for pedorthists when they are working with both systems to ensure proper fitting and comfort for patients.

The other options involve incorrect conversions, associating an inch with millimeters, meters, or kilometers rather than the centimeter measurement, which would not provide an accurate representation of an inch in the metric system.