Pottery shrinkage calculator
Convert wet, dry and fired dimensions using measurements from your own clay test bar or a known total shrinkage rate.
Each measured stage and total shrinkage must fall between -50% and 95%. No kiln settings, clay presets or dry-stage estimate from total shrinkage alone. Change the input or settings to update your result. Results update as you type. Up to 1,000,000 characters.
Your result
How to use Pottery shrinkage calculator
- Enter the measured inputs and select their units.
- Review the calculated dimensions, counts and rounding.
- Download the result and verify it against a sample before making the full project.
Useful next steps
Use a test bar from the same process
Enter measurements from the wet, dry and fired stages of the same test bar. Select the stage of the dimension you know. The calculator shows the equivalent dimensions at the other measured stages.
Keep stage percentages separate
A 100 mm wet bar that dries to 95 mm and fires to 85.5 mm has 5% drying shrinkage and 10% further firing shrinkage. The combined shrinkage is 14.5%, because percentages compound. Known total mode converts wet and fired dimensions only.
Save the calculation
Download a CSV of the results or instructions, a readable text report and a JSON report with values, formulas and assumptions. Calculations run locally on your device. Unit changes keep the numbers already entered, so check the selected units before using the result.