What is pottery clay shrinkage calculator?
Clay shrinkage is the size change that happens as clay dries and fires. Because shrinkage varies by clay body, firing temperature, forming method, and studio process, this calculator is a planning tool rather than a substitute for testing your own clay.
How to use this calculator
- Select or enter the shrinkage rate.
- Choose calculation direction.
- Enter the known dimension.
- Use the result as a starting size and test with your clay body.
How is it calculated?
Formula
wet size = fired size / (1 - shrinkage rate); fired size = wet size x (1 - shrinkage rate) What The Constants Mean
- Clay shrinkage presets (8% to 14%): Dropdown presets are planning examples; actual clay shrinkage should be tested in your studio.
A 6 in fired tile at 12% shrinkage should be made about 6.82 in wet.
Common mistakes
Published shrinkage rates are averages. Tile, lids, fitted forms, and repeatable production work need a shrink test because clay can shrink differently between drying and firing stages.
FAQ
How much does pottery clay shrink?
Many clay bodies shrink roughly 8% to 15%, but the exact rate depends on the clay and firing.
Do I use wet-to-fired or fired-to-wet?
Use fired-to-wet when you need to make a piece that finishes at a target size.
Should I test my clay?
Yes. Make a shrink ruler or test bar for accurate studio results.
Does firing temperature affect shrinkage?
Yes. Higher maturity often increases vitrification and shrinkage.