An anthropometer is a device designed for measuring the dimensions of the human body. The tool is usually used for determining the length of a section of the body such as an arm or head, not for determining the circumference. Typically, an anthropometer consists of a bar with two parallel sliding arms that can be moved to contain the part of the body being measured, thereby providing an accurate assessment of the distance between the two points. Throughout history, anthropometry has been used for a number of purposes, but the techniques have stayed essentially the same.
The essential function of an anthropometer is to determine the distance between two points accurately. In order to achieve this function, the device must be made of a material that is strong enough to retain its shape over many years, as the bending of the tool would render its measurements inaccurate. Not only must the arms of the anthropometer be parallel, but they must also be perfectly perpendicular to the ruler on which they slide. If these constraints are met, then the distance between the ends of the two arms when applied to the body will be accurately measured by the ruler.
While many body parts can be measured by an anthropometer, certain measurements have become conventional, and these devices have developed to easily accommodate these measurements. Measurements of the arms, head, foot, and fingers are all commonly accomplished by anthropometers. For example, a measurement across the skull, such as the distance between the temples, is facilitated with an anthropometer as this device gives accurate readings by physically touching the measurement points.
Even with the continued usefulness of anthropometers, it is possible and even practical to obtain detailed scans of human bodies in three dimensions using computers. As technologies improve and become less expensive, measurements by computer may completely replace anthropometer measurements because of the accuracy provided by machines.
Across history, anthropometers have been used in pseudo-scientific pursuits and attempts to scientifically assess man's nature. Infamously, physical measures were used during the Holocaust in an attempt to isolate the Jewish race from a Nazi perspective. Currently, anthropometry is primarily practiced to isolate average human body sizes for commercial products, as well as to study the effects of certain factors on human growth across populations.
Given the objectionable uses of anthropometry in history, it is understandable why many people object to being measured in this way, having viewed photographs of anthropometric tools in use in more sinister circumstances. As such, when using such a device, it is a good idea to be forthcoming about how the data will be used and why it is necessary.