Silicone Mold Calculator

The exact figure (box volume minus master volume) assumes every drop of mixed silicone ends up in the mold with zero loss. In practice silicone shrinks slightly as the two parts react, and pouring always leaves residue clinging to the mixing cup and stir stick. The 5% cushion is meant to prevent running out mid-pour, which on a two-part mold leaves a visible seam line where the pour stopped.

It estimates the silicone wall thickness on one side of the box by taking the master's footprint (approximated as masterVolumeCuIn divided by boxHeight, then square-rooted) and comparing it to your box width, then checking whether at least 0.5 inches of silicone remains on that side. It's a single-axis approximation, not a full 3D clearance check, so a master with an irregular or off-center shape can pass this check while still having a thin spot elsewhere.

Displacement is simply the master's volume as a share of the total box volume. A high displacement percentage means the master fills most of the box, leaving little room for silicone on any side — which is the same condition the Wall Ok check is flagging. Keeping displacement well under 50% generally leaves more margin for a sturdy, tear-resistant mold wall.

The volume math (box volume minus master volume, converted to fluid ounces) is material-agnostic and works for any rubber. But the gallons-to-pounds conversion uses silicone's typical density of about 10.3 lbs per gallon, so the weight output will be inaccurate for a rubber with a meaningfully different density — use the fluid ounce or gallon figures instead if you're working with something else.