Pressure Pot Sizing Calculator

Pressure casting forces trapped air bubbles down to a size too small to see by compressing the whole casting, and this calculator works out the two things that determine whether your setup can actually do that: whether the mold physically fits, and how hard to squeeze it. Fit comes first — the calculator adds 4 inches of clearance to your largest casting's diameter (room for the mold walls and the container itself) and 3 inches to its height (mold bottom plus lid clearance), then compares the resulting minimum pot volume against standard pressure pot sizes of 2.5, 5, and 10 gallons to recommend the smallest one that will hold your mold. Pressure comes second: each resin family has a different recommended working pressure to shrink bubbles below visible size — 40 PSI for polyester, 50 for epoxy, 60 for urethane — reflecting how these resins differ in viscosity and cure behavior under load.

The calculator also estimates your casting's own volume by treating it as a simple cylinder (using the same diameter and height you entered), which is handy for gauging how much resin you'll need but will overestimate a shape that isn't actually cylindrical — an irregular mold's true volume can be meaningfully smaller. A common mixup is entering the mold's outer dimensions instead of the casting's — since the pot needs to fit the whole mold, always measure to the mold's outer edge, not just the resin cavity, and always cross-check the recommended PSI against your specific resin manufacturer's datasheet, since formulations vary even within a single resin family.