Starting Clay Ball
1.38 lb
Wet Form
1.17 lb
Capacity
3.0 cups
Recommended Starting Weight
1.38
lb of wet clay
Wet Piece Weight
1.17 lb
Fired Weight
0.96 lb
Interior Capacity
3.0 cups
Clay Volume
13.0 cu in
Inputs
Result
Bowl shell volume ≈ 13.0 in³. Wet = 13.0 × 0.09 = 1.17 lb. Starting = 1.17 × 1.18 = 1.38 lb. Fired = 1.17 × 0.82 = 0.96 lb. Capacity ≈ 3.0 cups.
Inputs
Result
Cylinder shell + base + mug factor = 19.2 in³. Wet = 19.2 × 0.093 = 1.78 lb. Starting = 1.78 × 1.24 = 2.21 lb. Fired = 1.78 × 0.79 = 1.41 lb.
A standard 4-inch-diameter, 5-inch-tall mug with 1/4-inch walls needs about 2.2 lb of porcelain clay to start with. Stoneware needs slightly less because it has a lower wet density.
| Form | Starting Multiplier | Why |
|---|---|---|
| Bowl | 1.18× | Moderate trimming |
| Cylinder | 1.15× | Least waste |
| Mug | 1.24× | Trimming + handle clay |
| Plate | 1.16× | Rim shaping waste |
You always start with more clay than the final piece needs. Trimming, compression during throwing, and handle attachment all remove material from the original ball. The multiplier accounts for this loss.
Fired weight is typically 79–82% of wet weight, depending on clay body. Porcelain loses the most (21%), earthenware loses about 20%, and stoneware loses about 18%.
| Clay Body | Wet Density | Fired Factor | Shrinkage |
|---|---|---|---|
| Stoneware | 0.09 lb/in³ | 82% | ~12% |
| Earthenware | 0.087 lb/in³ | 80% | ~10% |
| Porcelain | 0.093 lb/in³ | 79% | ~15% |
Interior capacity depends on the inside radius, wall thickness, and form shape. A 6-inch bowl with 1/4-inch walls holds about 3 cups. Mugs show about 8% less capacity than cylinders of the same size due to handle attachment displacement.
Yes – wall thickness is one of the biggest factors. Doubling wall thickness from 1/4" to 1/2" can more than double the clay needed because volume scales with the squared difference between outer and inner radii.
Read our guide
Read our guide
Read our guide
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Last Updated: Mar 11, 2026
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