Clay Shrinkage Calculator

Created by Aleksandra Zając, MD
Reviewed by Wojciech Sas, PhD and Adena Benn
Last updated: Jan 03, 2023

Check the final dimensions in our clay shrinkage calculator if you're to craft clay or metal clay objects. Your piece will be smaller after drying - the thing is, how much smaller and how to calculate it. With the clay shrinkage calculator, you don't have to worry about it anymore. It doesn't matter if you use regular clay, metal clay, or air dry clay - shrinkage affects them all. Check also what material is used to reduce clay shrinkage, as it might also come in handy!

If you're into craft, be sure to also check our:

What is clay?

Clay is a form of soil made up of tiny particles of aluminum silicate. When moist, clay is malleable, and when it dries, it becomes hard and brittle, and you cannot mold it anymore. Clay is widely used as a material for bricks, tiles and pottery.

Clay shrinkage definition

When making pottery, remember that the final size will differ from what you've sculpted - it will be smaller. It's because of the clay shrinkage phenomenon.

Clay shrinkage is the process of shrinking the clay when it dries out. While drying, the water particles evaporate from the original mass, and the whole object becomes smaller. Clay shrinkage applies to all types of clay - regular clay, metal clay, and air dry clay.

Regular clay will shrink by 10%-20%. In metal clays, it strongly depends on the type and kind of the clay and varies from 5% to even 30%. Air-dry clay shrinkage has the narrowest range - the object will get 8%-12% smaller.

Clay shrinkage calculator use

Follow the steps:

  1. Measure your clay object before it dries out. We need all three dimensions - height, width, and length.
  2. Fill in the first three calculator rows with your measurements. Keep in mind that even though the basic unit is centimeters, you can change it to the most convenient unit.
  3. Now, put in the clay shrinkage percentage. It describes how much the ready objects will be smaller than the original ones. Regular clay has a 10%-20% shrinkage level, air dry clay - about 8%-12%. Metal clay shrinkage depends on the particular kind - check out the metal clay shrinkage chart to find the type you've used.
  4. Let the clay shrinkage calculator compute the results for you.
  5. That's done! You know what the dimensions of your object will be after you cure it.

Calculating clay shrinkage - formula to calculate shrinkage in clay

If you want to estimate the final dimensions on your own, here's the appropriate formula to calculate shrinkage in clay:

dimension=original dimension ×(1(CS100))\footnotesize \mathrm{dimension} = \mathrm{original}\ \mathrm{dimension}\ \times\left(1-\left(\frac{CS}{100}\right)\right)

where:

  • dimension\mathrm{dimension} - is the length, width, and height of your object after curing;
  • original dimension\mathrm{original~dimension} - is the length, width, and height of your object before it's cured - so this is what you've actually measured; and
  • CSCS - clay shrinkage percentage, expressed in percents (%), not as a fraction.

Move on to the How do I calculate 14 percent shrinkage on clay? question in our FAQ section to see how to put the formula to work.

What is metal clay? Metal clay shrinkage chart

Metal clay consists of metal particles (metals such as silver, gold, bronze, and copper) combined with water and an organic binder. We use metal clay mainly to make jewelry. When you fire metal clay objects in a kiln, the binder burns away, leaving pure metal particles.

Metal clay jewelry will shrink while burned as well. The level of shrinkage depends on the material used. Check the metal clay shrinkage chart for precise levels.

Brass

Type of clay

Shrinkage rate

Aussie brass (pink, vintage)

12-15%

Goldie lemon brass

9-15%

Bronze

Type of clay

Shrinkage rate

Aussie (Antarctic Moonlight/Sand, Desert Sun, Gold/Ruby Bronze, Iron Bark)

12-15%

Five Star Bronze (Regular, Light, Red, White)

12%-15%

Goldie Bronze (Hard/Soft/Mid)

8%-11%

Goldie de la Rosa Bronze

14%-19%

Goldie Roman Bronze

10%-12%

Goldie Sculptor's Bronze

9%-14%

Goldie Snow Bronze

16%-30%

Hadar's Clay

25%

Hadar's Quick-Fire Clay

10%

Hadar's One-Fire Bronze (also Brilliant Bronze)

15%

Hadar's One-Fire Champagne/Dark Champagne Bronze

30%

Hadar's One-Fire Rose Bronze

25%

Hadar's One-Fire Smart Bronze

24%

Hadar's Quick-Fire Brilliant/Rose Bronze

25%

Metal Adventures BronzClay

17%-20%

Metal Adventures FASTfire BronzClay

17%-20%

MetalMania Metal Clay

15%-19%

Prometheus (Regular, Sunny)

12%-13%

Prometheus Jeweller's Light Yellow

17%-19%

Prometheus Jeweller's Greenish Yellow

13%-14%

Prometheus Jeweller's Sterling White

15%-16%

Prometheus White Bronze

10%-12%

Copper

Type of clay

Shrinkage rate

Art clay

10%

Aussie/Aussie Snow White Copper

12%-15%

Cool Tool Cyprus Copper

20%

Goldie Copper

12%-18%

Goldie Sculptor's Copper

15%-23%

Hadar's One-Fire Copper

25%

Hadar's Quick-Fire Copper

25%

Metal Adventures COPPRclay

20%-22%

Metal Adventures White COPPRclay

20%-25%

Metal Mania Copper Clay

15%-19%

Prometheus Copper Clay

9%-10%

Gold

Type of clay

Shrinkage rate

Art Clay

15%

Mitsubishi Mat. PMC

11%

Iron

Type of clay

Shrinkage rate

Goldie Cherry Iron

9%-17%

Goldie Red Iron

12%-18%

Goldie Sunset Iron

8%-16%

Goldie White Iron

5%-11%

Goldie Yellow Iron

5%-14%

Platinum

Type of clay

Shrinkage rate

Mistubishi Mat. PMC

20%-30%

Silver

Type of clay

Shrinkage rate

Aussie .999/.960 Silver Clay

10%-12%

Aussie .999/.960 Silver Clay Super Flex

12%-15%

Art Clay new formula

8%-9%

Art Clay Standard and Slow-Dry

8%-10%

Art Clay 650 Low Fire and Slow-Dry

8%-9%

Art Clay Lite

10%

Metal Magic Silver

20%-25%

Mistubishi Mat. PMC Flex

10%-12%

Mistubishi Mat. PMC Original/Classic

25%-30%

Mistubishi Mat. PMC+ lump

12%-15%

Mistubishi Mat. PMC+ sheet

10%-12%

Mistubishi Mat. PMC3

15%-20%

Prometheus Silver Clay 950

15%

Prometheus Silver Clay 999

12%-13%

Silver Smiths' Metal Clay Powder

10%

Sterling silver

Type of clay

Shrinkage rate

Cool Tools EZ960 Sterling Silver

10%-11%

Metal Magic Sterling Silver

25%

Mistubishi Mat. OneFire Sterling PMC

13%-16%

Mistubishi Mat. PMC Sterling

15%-20%

Hadar's Clay One-Fire Steel XT

25%-30%

Hadar's Clay One-Fire Pearl Gray Steel

25%-30%

Hadar's Clay

10%-15%

Steel

Type of clay

Shrinkage rate

Hadar's Clay One-Fire Steel XT/Pearl Gray Steel

25%-30%

Hadar's Clay

10%-15%

Stainless steel

Type of clay

Shrinkage rate

Hadar's Clay/ Quick-fire Hadar's Clay

10%

FAQ

How do I calculate 14 percent shrinkage on clay?

To calculate the 14 percent clay shrinkage:

  1. Measure your object before it dries. You need all three dimensions: length, width, and height.
  2. Now, for the length, use the formula:
    final length = original length × (1-(CS/100))
    where CS is the clay shrinkage percentage.
  3. In our case, CS is equal to 14. So the formula looks like this:
    final length = original length × 0.86
  4. Use the same formula for width and height.
  5. Now you're done! Remember, you can double-check the results with our clay shrinkage calculator.

What material is used to reduce clay shrinkage?

To reduce clay shrinkage, you can use grog. Grog is clay that has already been fired and ground to various particle sizes. Usually, grog contains big particles, making it shrink less than typical clay.

How big will a 10 × 12 × 15 in piece of copper art clay be after drying?

The final dimensions of that piece will be 9, 10.8, and 13.5 in.

To calculate it, follow the steps:

  1. The copper art clay shrinkage rate is 10%.
  2. Use the formula:
    final dimension = original dimension × (1-(CS/100))
    where CS is 10%.
  3. Use the equation to calculate all the dimensions - length, width, and height.

How do I make homemade clay?

There are multiple recipes for homemade clay. This is an easy flour and salt clay (or salt dough) recipe:

  1. You need two cups of flour (~200 g), one cup of salt (~200 g), and 3/4 cup of water (~125 ml). You can add spices for coloring.
  2. Mix flour with salt, then add water and start stirring.
  3. Knead until it comes together into a ball.
  4. Your clay is ready!
  5. Let it dry at room temperature for about two days or put it into a low-heated (~212°F or 100°C) oven for three hours.

What can I make with air dried clay?

Here are some simple ideas for air dry clay objects:

  • Bowls;
  • Plant pots;
  • Vases;
  • Air-dry clay ring holders;
  • Fridge magnets of all kinds;
  • Christmas decorations to hang on a Christmas tree;
  • Earrings and necklaces.
Aleksandra Zając, MD
Original dimensions
Original length
in
Original height
in
Original width
in
Clay shrinkage
%
Usually 10%-20%. Using a metal clay? Check the metal clay shrinkage chart for the specific values.
Final dimensions
Final length
in
Final height
in
Final width
in
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