Every threshold below is taken from a named publication, shown with its paragraph and its status as of this page load. When a service changes the standard, the tool changes with it — which is the whole point, because most military calculators on the web are still applying a standard that has since been rescinded.
The Army's current standard is a waist-to-height ratio under 0.55. Enter waist and height in the same units.
The Marine Corps standard is a waist-to-height ratio of 0.52, stricter than the Army's 0.55. Waist and height are each rounded down to the nearest 1/2 inch first.