Plaster Calculator

Calculate the amount of water and plaster you will need for various solid forms.

Bookmark this link on your phone’s browser for easy access!

The code is open source and available on Github:

Inspired by Keith Simpson’s (@earlyamericanrobotpottery) plaster handout and the USG plaster calculator.

The calculations are from USG (, Keith Simpson (Alfred University), and Andrew Martin (“The Essential Guide to Mold Making & Slip Casting”).