Clay Shrinkage Calculator

Calculate final dimensions after drying and firing.

Wet Height: Please enter a valid height.

Wet Width: Please enter a valid width.

Wet Depth: Please enter a valid depth.

Drying Shrinkage (%): Please enter drying shrinkage %.

Firing Shrinkage (%): Please enter firing shrinkage %.

Unit:

How It Works

Final Dimension = Wet Dimension × (1 – Drying Shrinkage/100) × (1 – Firing Shrinkage/100)

Clay shrinkage is a basic but important concept that every ceramic artist and potter should understand. When clay dries and goes through the firing process, all the water in it evaporates and chemical changes occur that cause the clay to shrink. This natural process directly affects the final size of the ceramic piece. Therefore, if you are making a pottery, sculpture, or functional item, it is important to calculate shrinkage beforehand using this Clay Shrinkage Calculator so that the final product is exactly the size you desire.

What is Clay Shrinkage?

Clay shrinkage occurs in two main stages: drying and firing. During drying, water evaporates from the clay, bringing the particles closer together and causing shrinkage. In the firing stage, the high temperature of the kiln further compacts the clay as it vitrifies (becomes glassy), causing further shrinkage. The amount of shrinkage depends on a number of factors, such as:

Clay type: Different clays, such as earthenware, stoneware, or porcelain, have different shrinkage rates—usually around 10-15%.
Firing temperature: The higher the temperature, the more the shrinkage. Porcelain will shrink even smaller if baked at 1300°C.
Clay moisture: Wet clay will shrink more because water will be used up during drying.

It is important to understand all of these things, especially if you are making lids, sets, or something of a specific size. These factors have to be kept in mind to control the size of the final product!

How to Use the Clay Shrinkage Calculator?

The biggest challenge when working with pottery is estimating how much the clay will shrink after drying and firing. We created this tool to make your job easier. To use this calculator correctly, please follow all the steps below:

Step 1: Enter Wet Dimensions

First, measure the Height, Width, and Depth (thickness) of your wet clay project. Enter these values in the first three boxes. (Note: If you only want to see the height, enter dummy numbers in the other boxes to avoid errors).

Step 2: Enter Shrinkage Percentage

Every clay body is different. Based on the information provided on your clay packet or by your supplier:
Drying Shrinkage: The percentage of size reduction after the clay dries (e.g., 5%).
Firing Shrinkage: The percentage of size reduction after firing in the kiln (e.g., 10%). Enter both of these values.

Step 3: Select Units

Choose from the dropdown menu whether you took your measurements in Centimeters (cm) or Inches (in).

Step 4: Press the Calculate Button

After filling in all the details, click the "CALCULATE" button. If any box is left empty, an error message will be displayed.

Step 5: View the Final Result

Once you press the button, you will see the Final Dimensions below. This is the size that will remain after drying and firing are complete.

Pro Tip: If you are unsure how much your clay will shrink, make a test tile first to check the shrinkage percentage, then use that percentage here for accurate results.

Example Calculation

Suppose you have a wet clay piece measuring 20 cm in length and 15 cm in width. After drying, it measures 18 cm in length and 13.5 cm in width. You plan to fire it at 1200°C (mid-fire). Here’s how the calculator processes this:

Length Shrinkage: ((20 – 18) / 20) * 100 = 10%
Width Shrinkage: ((15 – 13.5) / 15) * 100 = 10%
Average Shrinkage: (10 + 10) / 2 = 10%
Fired Dimensions: Using a firing shrinkage factor based on the temperature, the calculator estimates the final length and width (e.g., approximately 16.2 cm and 12.15 cm, respectively).
Volume Shrinkage: Calculated assuming depth equals width, providing an approximate volume reduction.

These results help you anticipate the final size of your piece and plan accordingly.

The Formula (The logic behind this calculator)

Clay shrinkage doesn't happen all at once; it's a sequential process.

First, wet clay shrinks when it dries (Drying).
Then, that dried clay shrinks further when fired in a kiln (Firing).

Therefore, the formula is:

Why Use a Clay Shrinkage Calculator?

This Clay Shrinkage Calculator makes the job of ceramic artists much easier, saving time and trial-and-error. Check out its advantages:

Correct Measurements: Exact calculations will result in perfect size for your ceramic pieces (such as lids, tiles).
Time Saving: Calculating the shrinkage of clay reduces both the time and effort.
Useful: No matter what type of clay you use or fire at different temperatures, this Clay Shrinkage Calculator adjusts easily. If your kiln is slightly different, you can even enter custom settings.
You will learn: It does not matter whether you are new or an experienced potter, the tips and explanations provided here make understanding the shrinkage of clay even simpler.

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Tips for Managing Clay Shrinkage

To maximize the calculator’s benefits, consider these best practices for working with clay shrinkage:

Test your clay: Each clay has a different shrinkage rate. Before starting a large project, test a small sample to see how much shrinkage will occur.
Think about multi-piece projects: If you are making a jar and a lid, calculate the shrinkage of both pieces. Otherwise, it won’t fit later—the lid will be too small or too large!
Make notes: Write down the shrinkage rate of each clay type and firing temperature in a diary. It will come in handy later, brother!
Understand the effect of firing temperature: More heat (such as 1300°C for porcelain) = more shrinkage. So, wet clay will have to be kept a slightly larger size.
Keep the measurements accurate: Measure the clay accurately in both wet and dry states. Put the correct data in the calculator, otherwise the result will be wrong!

Clay Shrinkage Calculator is the perfect tool for pottery lovers that helps you make perfect size ceramic pieces by accurately calculating the shrinkage after firing the clay. It not only eliminates guesswork but also saves you time. Whether you are a hobbyist or a professional, its easy-to-use design and accurate results allow you to confidently plan your projects, reduce mistakes, and share your experiences with the pottery community… So don’t stop experimenting now, try this calculator and improve your pottery skills even more.

If you would like to learn more about clay shrinkage, you can visit this website.

Frequently Asked Questions

How do you calculate clay shrinkage?

The simple formula for calculating it is: (Wet Size - Dry Size) ÷ Wet Size × 100. However, for the most accurate result, you need to add the shrinkage from both drying and firing separately, which our clay shrinkage calculator does automatically.

What is the average shrinkage percentage of clay?

It depends on the type of clay body. Generally: Earthenware: 8% - 12%, Stoneware: 10% - 14%, and Porcelain: 12% - 15%, which shrinks the most.

Does clay shrink more during drying or firing?

In most cases, clay shrinks more during drying (approximately 5-7%), because water evaporates during this process. During firing, the particles fuse together, so there is slightly less shrinkage (3-6%), unless you are using porcelain.

If I want the final mug to be 10cm tall, how big should I make it when it's wet?

For this, you need to know the shrinkage rate. Let's assume the total shrinkage is 12%. The formula would be: 10cm ÷ (1 - 0.12) = 11.36cm. So, you would need to make the wet clay piece 11.36cm tall.