How much does clay shrink when fired?

Total shrinkage (drying plus firing) ranges from 8% for low-fire earthenware to 18% for high-fire porcelain. Stoneware at mid-fire (cone 6) typically shrinks 10-12% total. The exact amount depends on the specific clay body and firing temperature.

Does shrinkage happen evenly?

Shrinkage should be even in all directions, but uneven thickness or drying can cause uneven shrinkage, leading to warping or cracking. Pieces with even wall thickness and slow, even drying shrink most uniformly.

How do I test my clay shrinkage rate?

Make a test tile and score a line exactly 10cm long when wet. After drying, measure the line. After firing, measure again. The percentage of reduction is your shrinkage rate. For example, if 10cm becomes 8.8cm, shrinkage is 12%.

Why should I calculate wet size rather than just making it bigger?

Guessing leads to inconsistent results. If you need lids to fit pots, sets to match, or specific sizes for commissions, calculating the exact wet dimensions ensures the finished piece is the right size after shrinkage.

CraftCalcs

Pottery Shrinkage Calculator

Calculate wet clay dimensions needed to achieve desired finished size after firing shrinkage.

Desired Finished Length

Target length after firing

Desired Finished Width

Target width after firing

Desired Finished Height

Target height after firing

Clay Type

Type of clay body

Firing Temperature

Kiln firing temperature range

How We Calculate This

Shrinkage Factor

Wet Size = Desired Size / (1 - Shrinkage%/100)

Total Shrinkage

Total = Drying Shrinkage + Firing Shrinkage

Drying shrinkage occurs as water evaporates from wet clay. Firing shrinkage occurs as clay particles vitrify at high temperature.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Always verify quantities before purchasing materials.