Clay Shrinkage Percentage Calculator
Measure the same feature on a piece before and after firing to find your clay body’s actual shrinkage percentage.
Measure a wet and fired size
Use the same unit for both (inches, cm, mm — the math doesn’t care which, only that they match).
Shrinkage: 12%
Frequently asked questions
- How do I measure my clay's shrinkage percentage?
- Mark a line of a known length (e.g. 10cm) on a test tile while it's wet, then measure that same line after the final firing. Shrinkage % = (wet length − fired length) ÷ wet length × 100.
- Why test my own clay instead of using a published number?
- Shrinkage varies by manufacturer, clay body, and firing temperature — even two bags of the same product line can differ slightly. A test tile fired in your own kiln to your own cone is the only truly accurate number for your work. Use the reference chart for planning, and test for anything precise.
- Does it matter what unit I measure in?
- No — shrinkage percentage is a ratio, so inches, centimeters, or millimeters all give the same result as long as you use the same unit for both measurements.