Perm Rod Selection Calculator

Rod Diameter is built in two lookup steps, not one: Target Curl Size sets a base diameter (0.25in for a tight ringlet up to 1.0in for a body wave, lines 11-14), then Hair Texture nudges that base by exactly 1/16 of an inch -- coarse hair adds 0.0625in, fine hair subtracts it, medium leaves it unchanged (lines 17-18). Because both inputs only offer a handful of discrete options, Rod Diameter can only ever land on one of twelve exact values across all combinations, and Rod Size / Color is bucketed from that value against fixed boundaries (lines 21-25) -- the "Jumbo" label is reachable from exactly one combination, Body Wave paired with Coarse hair (1.0625in), and nothing else. Rods Needed defaults to a fixed count keyed only to Target Curl Size -- 50 rods for tight ringlet or medium curl, 36 for anything looser (line 28) -- unless Override Rod Count is set above zero, in which case your typed number replaces that recommendation entirely; leaving it at zero (the default) is what triggers the automatic figure, not a separate toggle.

Wrapping Technique is the only place Hair Length is read at all: over 10 inches recommends spiral wrap, 6 to 10 inches allows either croquignole or spiral, and 6 inches or under recommends croquignole only (lines 31-32) -- Hair Length has no effect on Rod Diameter, Rods Needed, Processing Time, or Expected Curl Circumference. Section Width and Section Depth are both derived purely from Rod Diameter (Section Depth is 75% of it, line 36), and Expected Curl Circumference is Rod Diameter times pi times a fixed 1.5 relaxation factor (line 42).