Clay Shrinkage Calculator

Calculate how large your pottery piece should be based on how much your clay shrinks as it dries and is bisque and glaze fired*. Enter your clay's shrink rate, and the desired final dimensions. Also helpful for making replacement lids!

Or, diameter for bowls or re-making lids...

*Use the entry fields above to enter the final dimensions that you want your pottery piece to be after it is bisqued and glaze fired. Based on your clay's shrink rate, the online clay shrinkage ruler will then reverse calculate the approximate size that your piece should be in the greenware state (ie. before it dries and is kiln fired).

Keep in mind that as with any shrinkage ruler, these calculations are approximations and the final piece may be slightly larger or smaller. Several factors, including firing time and temperature, can vary slightly per kiln, which can impact the actual shrinkage.

Determining Clay Shrinkage

The clay manufacturer or distributor should have specs, including clay shrinkage at the various firing temperatures. If you work in a studio, they will likely have this information, and, if you buy your own clay, check with the ceramics store.

You can also run your own test on how much your clay shrinks, using our Clay Shrink Test Calculator.

Make Bigger Pots, Replacement Lids

If you've ever been surpised by the diminished size of your piece when it comes out of the glaze kiln, this reverse clay shrink calculator can help you make pottery that's very close to the size you want.

Another advantage of this shrink calculator is for making replacement lids. For example, if your teapot lid breaks, you can reverse calculate the lid's size based on the finished teapot's lid area.