Reference: MIL-HDBK-759, Human Factors Engineering Design for Army Materiel. Human factors engineering must be included in equipment design to minimize maintenance problems and optimize work performance. Social factors engineering relates to man’s size, strength, and other capabilities to the operation of equipment and the production of work.
Ironically, anthropometric data are collected in metric measurements; the problem has been the accurate conversion to U.S. customary units. The required adoption of the metric system will solve this problem. However, during the transition period, it may be necessary to convert from the SI system of units to the U.S. customary units. Figs. 7-1 and 7-2, taken from MIL-HDBK-759, show anthropometric data in both the SI and U.S. conventional units. The conversion method using data from Figs. 7-1 and 7-2, though simple, is illustrated in the paragraphs that follow.
Rules for the use of prefixes in par. 3-3 states that the preferred designations are those representing multiples or submultiples of 103; i.e., for length, one should use km, m, mm, ^m, etc. However, in the case of body measurements, the centimeter is a very convenient unit; for example, consider the combinations 98-64-91 cm as compared with 980-640-910 mm. In the clothing industry and the medical field, measurements of the human body are taken more frequently in centimeters than millimeters. Thus centimeters are used in Figs. 7-1 and 7-2.
The linear dimensions — in this example from centimeters to inches — are converted as described in par. 4-1 using unit equality 1 in. = 0.0254 m from Table 5-1 or 5-2. Use also is made of the relationship 1 cm= 0.01 m from Table 2-4. Thus for the chest depth measurement of 18.9 cm for the 1 st percentile in Fig. 7-1 and go to this URL for more info.