a studio tool
clay shrinkage calculator.
Clay shrinks twice, drying and firing, by 10 to 15 percent all up. That generous mug becomes a modest one. Work it both ways below, then read clay bodies explained for why.
Most stoneware shrinks 10 to 15 percent wet to fired. Your clay's bag lists its figure; test tiles confirm it.
wet → fired
What a fresh measurement becomes out of the kiln.
88.0mm fired
target → throw
How big to make it wet to land on the size you want.
102.3mm wet
common questions
how much does clay shrink when fired?
Most stoneware shrinks 10 to 15 percent from wet to fired, across drying and firing combined. Porcelain can shrink more. The exact figure is on the clay's bag and confirmed with test tiles.
how do i calculate pottery shrinkage?
Fired size = wet size x (1 - shrinkage%). To hit a target fired size, throw it at target ÷ (1 - shrinkage%). This calculator does both directions for you.
why does my lid not fit after firing?
Lid and pot shrink independently, and small differences in wall thickness or drying change the rate. This is why potters make lids and galleries together, from the same clay, and measure with shrinkage in mind.