Pottery Shrinkage Calculator

About this calculator

Clay shrinks as it dries and again as it fires, so a potter has to throw or build a piece larger than the target finished size. The math inverts the standard shrinkage formula — shrinkage% = (wet size − fired size) ÷ wet size — to solve for wet size = fired size ÷ (1 − shrinkage%). Typical shrinkage runs about 10-13% for stoneware clay bodies and can reach 15%+ for some porcelains, and every clay's specific rate is usually listed on the bag or test-tile data from the supplier.

Studio potters and ceramicists use this before throwing a functional piece like a mug or bowl that needs to fit a specific lid, stack with a set, or hit a precise finished diameter, while production potters use it to keep a whole batch consistent across the wet-to-bisque-to-glaze-fire shrink cycle.