What is shrinkage percentage in ceramics?

Shrinkage percentage measures how much a clay piece contracts from one state to another. Wet-to-fired shrinkage = ((wet − fired) / wet) × 100. A 12% shrinkage means a 100 mm wet piece will fire to 88 mm.

How much does clay shrink when fired?

Most commercial clays shrink 10–15% from wet to fired. Stoneware typically shrinks 12–14%, earthenware 8–12%, and porcelain can shrink up to 15–18%. Your clay body's data sheet will list its rated shrinkage.

Why measure the same dimension each time?

Clay shrinks uniformly in all directions, but measuring the same edge or diameter eliminates any shape-change errors. A straight edge or a set calipers applied to the same point gives the most accurate result.

What is dry-to-fired shrinkage?

Dry-to-fired (or "firing") shrinkage is how much a bone-dry piece contracts during the kiln firing. It is separate from drying shrinkage (wet-to-dry) and indicates how much vitrification and densification occurs in the fire.

Can I use this calculator for glazed pieces?

Yes, but measure the clay body itself, not over glaze. Measure before glazing (bone-dry or bisque) and after the glaze fire. Glaze thickness can add a small amount to the outside dimension; for most work this difference is negligible.

Clay Shrinkage Calculator

Name: Clay Shrinkage Calculator
Availability: InStock
Author: Nham Vu

Enter wet, dry, and fired clay dimensions to get shrinkage percentages for each stage instantly.

Mode

Unit

mm cm in

Wet Size

Dry Size (bone-dry)

Fired Size

Optional — leave blank to calculate wet-to-dry only.

Results

Enter measurements on the left to see shrinkage.

Measure the same dimension at each clay stage.

Summary

Enter wet, dry, and fired clay dimensions to get shrinkage percentages for each stage instantly.

How it works

Measure the length (or width) of your piece in the wet state right after forming.
After bone-dry, measure the same dimension and enter it in the Dry Size field.
After firing, measure the same dimension and enter it in the Fired Size field.
The calculator instantly shows wet-to-dry shrinkage, wet-to-fired shrinkage, and dry-to-fired shrinkage.
Use the Required Wet Size mode to work backwards: enter your target fired size and known shrinkage rate to get the wet dimension to throw.

Use cases

Determine how large to throw a bowl so it fires to a specific diameter.
Test a new clay body to document its shrinkage rate for future reference.
Compare wet-to-dry and dry-to-fired stages to identify where a clay body shrinks most.
Work backwards from a commissioned piece size to find the correct wet throwing size.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu