Clay & Shrinkage

Target Finished Size Calculator

Calculate the wet throwing size needed to achieve a specific finished fired dimension.

Reviewed by ClayCalc Editorial · Updated

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Results

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Enter your measurements above and click Calculate.

Formula Explanation

To achieve a specific fired dimension, you must throw (or build) the piece larger to account for the measured total shrinkage from the making size to the final fired size.

Wet Size = Final Size ÷ (1 − shrinkage% ÷ 100)

Common Mistakes

  • cancel Using an inaccurate shrinkage rate. The result is only as good as your shrinkage data. Always test your specific clay body and firing cone — don't rely solely on the manufacturer's stated shrinkage.
  • cancel Applying one shrinkage rate to all directions. For functional lids and galleries, measure shrinkage in both the horizontal and vertical axes separately.

Method & review note

About this calculation

Uses measured dimensions or weights and a stated arithmetic model. Clay and forming method vary, so production decisions should use test pieces from the actual body and firing.

Reference: Digitalfire — Drying Shrinkage. See the editorial methodology for testing, precision and corrections.

Input handling: Values are sent to the ClayCalc server for this request and are not written to the application database.

Read the Clay Shrinkage Test

Frequently Asked Questions

Does the wet size include a correction factor? expand_more
No. The calculator applies the stated total shrinkage directly: wet size = final size ÷ (1 − shrinkage rate). Use a shrinkage rate measured from your own clay and process.
Can I use this for slab work as well? expand_more
Yes. Enter the desired finished slab dimension and apply your clay body’s total shrinkage rate. For directional work, calculate horizontal and vertical axes separately if your clay shows anisotropic shrinkage.
Should I throw bigger or smaller for lids? expand_more
The calculated value is a starting point. Add a deliberate fitting allowance based on your lid design and test your own clay and firing rather than relying on a universal millimetre addition.