What is clay shrinkage and why does it matter?
All clay shrinks as it dries and again as it fires. The total shrinkage from wet to glaze-fired ranges from around 5% for earthenware to 16% for fine porcelain. If you don't account for this, a piece made to the finished dimensions you want will end up smaller after firing.
These tools help you work with shrinkage precisely: measure your clay's actual rate with a test bar, generate a printed ruler that already accounts for it, or convert any measurement between wet and fired dimensions.
Start with your clay's actual shrinkage rate
Supplier figures are useful starting points, but forming method, firing schedule, and even clay batch variation affect the final number. Use the test bar guide to measure your own clay, then enter that percentage into any of the tools above.