Armature Design Calculator

Main rod diameter is chosen from five fixed sizes assigned to height brackets (up to 18 in, 36 in, 48 in, 72 in, and above), not from a smooth formula, because armature rod only comes in a handful of practical stock diameters. Any two heights that fall in the same bracket -- say 20 inches and 34 inches, both in the "up to 36 in" tier -- get the identical recommended diameter, which is expected rather than a rounding artifact.

Sculpting medium changes only the estimated clay/wax weight, by applying a different density per cubic inch for water-based clay, oil-based clay, and sculpting wax. It does not change any of the armature's structural recommendations -- rod diameter, wire diameter, or base plate sizing are driven entirely by the sculpture's height, width, and depth, not by which medium is selected.

Form type sets two things: the fill factor used to estimate sculpture volume from the bounding box (a human figure, animal, and abstract form each occupy a different share of their bounding box), and the limb multiplier used to estimate total rod length, since a quadruped needs more internal support length for four legs than a single abstract mass of similar bounding dimensions.

Estimated clay/wax weight scales with height, width, and depth in the same direction and by comparable magnitude, because it is derived from bounding-box volume (height times width times depth) times a fill factor. Doubling any one dimension roughly doubles the estimate, and increasing all three compounds multiplicatively rather than additively, since volume is a product of the three.