Clay Shrinkage Calculator

This easy to use clay shrinkage calculator is an essential tool for ceramicists, potters, and sculptors to predict the final dimensions of their clay creations after firing.

For example, if you have a clay piece with an initial length of 10 inches and a known shrinkage rate of 12% (0.12), the calculator would determine the final length as:

Final Length = 10 × (1 - 100 × 0.12)
             = 10 × (1 - 12)
             = 10 × 0.88
             = 8.8 inches

Project	Clay Type	Shrinkage Rate	Initial Size (cm)	Final Size (cm)
*Vase*	*Porcelain*	*15%*	30	*25.5*
*Dinner Plate*	*Stoneware*	*11%*	25	*22.25*
*Sculpture*	*Earthenware*	6%	50	47
*Mug*	*Terra Cotta*	7%	12	*11.16*
*Tile*	*Ball Clay*	*18%*	10	*8.2*

Clay Shrinkage Chart

Clay Type	Shrinkage Rate	Initial Size (inches)	Final Size (inches)
Porcelain	15%	12	10.2
Stoneware	12%	12	10.56
Earthenware	8%	12	11.04
Terra Cotta	7%	12	11.16
Ball Clay	20%	12	9.6

Clay Shrinkage Formula

The formula for calculating clay shrinkage is:

Final Dimension = Initial Dimension × (1 - Shrinkage Rate)

Initial Dimension: The size of your piece when first formed
Shrinkage Rate: Expressed as a decimal (e.g., 0.10 for 10%)
Final Dimension: The resulting size after firing

The formula can be rearranged to solve for different variables:

To find the Final Dimension: Final Dimension = Initial Dimension × (1 – 100 × Shrinkage Rate)
To find the Initial Dimension: Initial Dimension = Final Dimension ÷ (1 – 100 × Shrinkage Rate)
To find the Shrinkage Rate: Shrinkage Rate = (1 – Final Dimension ÷ Initial Dimension) ÷ 100

How to Calculate Clay Shrinkage?

To accurately calculate shrinkage:

Measure the initial dimensions of your clay piece.
Determine the shrinkage rate of your clay (usually provided by the manufacturer).
Apply the shrinkage formula: Final Dimension = Initial Dimension × (1 – 100 × Shrinkage Rate)
Calculate the result to find the final dimension.

For example, let’s calculate the shrinkage of a clay bowl with an initial diameter of 8 inches, using a clay with a 10% shrinkage rate:

Final Diameter = 8 × (1 - 100 × 0.10)
               = 8 × (1 - 10)
               = 8 × 0.90
               = 7.2 inches

The bowl’s diameter will shrink from 8 inches to 7.2 inches after firing.

How Much Does Clay Shrink By?

Generally, clay shrinkage ranges from 4% to 20%.

Earthenware: 4-8%
Stoneware: 9-13%
Porcelain: 14-20%

Clay shrinkage varies significantly based on several factors:

Clay Body Composition: 8-15% typical range
Firing Temperature: Higher temperatures = more shrinkage
Particle Size: Finer particles typically shrink more
Water Content: More water = greater shrinkage

What is the Shrinkage Limit of Clay?

The shrinkage limit represents the maximum amount a clay body can shrink. Different clay types have varying limits:

Porcelain: 12-16%
Stoneware: 10-13%
Earthenware: 6-8%
Ball Clay: 8-12%

The shrinkage limit of clay refers to the maximum amount of water that can be removed from the clay without causing a decrease in its volume. This concept is crucial in soil mechanics and geotechnical engineering.

For pottery and ceramics, the shrinkage limit is less relevant than the overall shrinkage rate. However, understanding this limit can help potters avoid excessive cracking or warping during the drying process.

To calculate the shrinkage limit:

Measure the volume of a wet clay sample.

Dry the sample completely.

Measure the volume of the dry sample.

Calculate the shrinkage limit using the formula: Shrinkage Limit = (Volume of Wet Sample – Volume of Dry Sample) ÷ Volume of Dry Sample × 100

If a wet clay sample has a volume of 100 cm³ and shrinks to 85 cm³ when dry:

Shrinkage Limit = (100 - 85) ÷ 85 × 100
                = 15 ÷ 85 × 100
                ≈ ***17.65%***

This means the clay can lose up to 17.65% of its volume before reaching its shrinkage limit.

Sources / References

Related Tools:

Clay Shrinkage Calculator – Calculate Clay Shrinkage Limits in Ceramics