Clay shrinkage calculator
A 4" fired mug isn't thrown at 4". Convert either direction, in any unit.
Throw it at
4.55
fired = thrown × (1 − shrinkage/100). Shrinkage compounds drying + firing; use your clay body's measured total, not the bag estimate, once you have test tiles.
Typical total shrinkage by clay body
| Clay body | Wet → fired |
|---|---|
| Stoneware (cone 6-10) | 10-14% |
| Porcelain | 12-16% |
| Earthenware / terracotta | 6-10% |
| Raku bodies | 8-12% |
Shrinkage happens twice — drying shrinkage as water leaves, then firing shrinkage as the body vitrifies — and the bag's number is a lab average. Throw a 10 cm test tile, measure it fired, and use your measured total: it's the difference between a dinner set that stacks and one that almost does.
Claybench stores measured shrinkage per clay body
Every form you plan carries the right throwing size automatically.