Snap & Rivet Sizing Calculator

This calculator sizes hardware around one physical constraint: the snap or rivet post has to be long enough to clear the leather stack and still fold or peen over cleanly on the back side. Total Thickness drives that directly -- Minimum Post Length is always Total Thickness plus about 3mm (1/8 in) of grip allowance, the standard rule of thumb across the leathercraft trade for how far a post should stand proud of the stack before it's set, so Minimum Post Length rises in exact lockstep with how thick your combined layers are. Recommended Post Length then rounds that minimum up to the nearest commercially available post length (6, 8, 10, 12, 15, 18, or 20mm), which is why its value plateaus over a band of thickness inputs and then steps up a full size once you cross into the next stocked length.

Snap Type controls an entirely separate group of outputs: Cap Diameter and Hole Punch Size are fixed by which line you pick (Line 20, Line 24, or Line 16), each corresponding to a standard snap cap diameter used across the leathercraft trade, and neither of those two outputs responds at all to Total Thickness. In short, thickness sizes the post length and Snap Type sizes the cap and punch -- the two halves of the calculation never interact.