The pottery clay weight calculator estimates how much clay you need by project type and final dimensions. Clay shrinks 10–15% when fired, so this tool accounts for shrinkage to help you start with the right amount of wet clay.
Clay Weight Estimator
Estimate clay needed including shrinkage allowance
How to Use the Pottery Clay Weight Calculator
The pottery clay weight calculator estimates the wet clay weight you'll need to start a project, accounting for the shrinkage that occurs during drying and firing. Different clay bodies shrink different amounts — porcelain shrinks the most, earthenware the least.
Step 1: Select your project type
Choose the project type closest to what you're making. Bowls and plates use less clay than their volume suggests because they're formed from flat slabs or pulled thin. Mugs and cylinders are similar. Solid sculptures use significantly more clay — the tool calculates assuming roughly 50% solid fill for sculptures with hollow walls. Slab work uses a straightforward length × width × thickness calculation.
Step 2: Enter finished dimensions
Enter the dimensions you want your fired, finished piece to be. The calculator will add extra clay to account for the shrinkage that happens during firing. A stoneware bowl that shrinks 12% needs to be formed 12% larger in all directions — so what starts at 9 inches in diameter finishes at about 8 inches.
Step 3: Choose your clay body's shrinkage rate
Check your clay's data sheet for the exact shrinkage rate (usually listed as a percentage). Earthenwares typically shrink 8–10%, stoneware 10–14%, porcelain 12–16%. Most wheel-thrown work uses stoneware, so 12% is a reasonable default. Your studio may have test tiles showing actual shrinkage for specific clay bodies.
FAQ
Is this clay weight calculator free?
Yes, completely free with no signup required. Enter your piece dimensions and get an instant clay weight estimate.
Is my data safe and private?
Yes. All calculations run locally in your browser. No data is sent to any server.
How much does clay shrink when fired?
Shrinkage varies by clay body: earthenware shrinks 10–12% in total (wet to fired), stoneware 12–15%, and porcelain 14–18%. Fine porcelain can shrink up to 20%. Shrinkage happens in two stages: drying (leatherhard to bone dry) and firing (bisque and glaze fire). This calculator accounts for total shrinkage from wet clay to final fired dimensions.
How do I calculate clay weight for a specific piece?
Estimate the volume of clay needed based on your target fired dimensions, then add the shrinkage factor to get the wet clay volume. Clay density is approximately 1.8–2.0 g/cm³. The calculator handles these conversions using typical wall thickness for different project types and adjusts for the clay body's shrinkage rate.
What is the difference between earthenware, stoneware, and porcelain?
Earthenware fires at low temperature (1800–2100°F / 980–1150°C), is porous unless glazed, and has 10–12% shrinkage. Stoneware fires at mid to high temperature (2100–2400°F), is dense and vitrified, with 12–15% shrinkage. Porcelain fires at high temperature (2300–2400°F), is translucent when thin, very dense, with the highest shrinkage at 14–18%.
Can I reuse clay scraps?
Yes — leatherhard and bone dry clay can be reclaimed by breaking it up, soaking in water until completely dissolved, spreading on plaster bats or absorbent surfaces to dry to throwing consistency, then wedging to remove air bubbles. Already-fired clay (bisque or glaze fired) cannot be reclaimed — it's permanent once fired.