Clay Weight Calculator
How much wet clay a wheel thrown or hand built form needs, worked out from the surface area and the wall thickness.
At a glance
- What you enter
- Outside diameter, Height, Wall thickness, Wet clay density, Fired clay density, Linear shrinkage, Throwing and trimming loss
- What you get
- Wet clay in the finished wall, Wet clay to prepare, Wet clay to prepare, Wet clay if the form were solid, Weight of the fired piece, Volume of clay in the wall, Total surface area of the shell, Fired outside diameter, Fired height, Capacity if the form were a closed cylinder, How many times a solid volume guess would overstate the clay
- Formula shown
- Yes, every step, right below your results.
- Cost and privacy
- Free, no account needed, and nothing you type is stored.
See worked examples ↓ Read the FAQ ↓ Share this calculator ↓
Results are estimates for general information only, always verify with a professional or official source before acting on them.
How to use the Clay Weight Calculator
- 1 Enter Outside diameter (cm), The widest point of the form as it will come off the wheel or be built.
- 2 Enter Height (cm)
- 3 Enter Wall thickness (mm), Six to ten millimetres for a thrown domestic pot. Enter half the smallest dimension for a solid form.
- 4 Enter Wet clay density (g per cubic cm), Stoneware is about 1.8 to 2.0 as wet clay. Porcelain is slightly denser, a heavily grogged body slightly lighter.
- 5 Enter Fired clay density (g per cubic cm), About 2.0 to 2.2 for a fired stoneware. The fired figure is higher because the body has lost the water and closed up.
- 6 Enter Linear shrinkage (%), Five to twelve percent from wet to fired, with seven a common mid range figure.
- 7 Enter Throwing and trimming loss (%), Clay that becomes slip on your hands, trimmings or a collapse. Ten to fifteen percent is normal.
- 8 Press Calculate. You get Wet clay in the finished wall, Wet clay to prepare, Wet clay to prepare, Wet clay if the form were solid, Weight of the fired piece, Volume of clay in the wall, Total surface area of the shell, Fired outside diameter, Fired height, Capacity if the form were a closed cylinder, How many times a solid volume guess would overstate the clay, and every intermediate step stays visible under "How is this calculated?"
- 9 Change one number at a time to see what moves the result, that is usually the most useful thing a calculator can tell you.
Worked examples
Real numbers run through this calculator. Open any example to load it into the form above and change it.
A mug sized cylinder
A 10 cm diameter, 12 cm tall cylinder with an 8 mm wall.
You enter
- Outside diameter
- 10 cm
- Height
- 12 cm
- Wall thickness
- 8 mm
- Wet clay density
- 2 g per cubic cm
- Fired clay density
- 2.15 g per cubic cm
- Linear shrinkage
- 7%
- Throwing and trimming loss
- 12%
You get
- Wet clay in the finished wall
- 728.85 g
- Wet clay to prepare
- 816.31 g
- Wet clay to prepare
- 0.82 kg
- Wet clay if the form were solid
- 1,884.96 g
- Weight of the fired piece
- 783.51 g
- Volume of clay in the wall
- 364.42 cu cm
- Total surface area of the shell
- 455.53 sq cm
- Fired outside diameter
- 9.30 cm
- Fired height
- 11.16 cm
- Capacity if the form were a closed cylinder
- 0.76 L
- How many times a solid volume guess would overstate the clay
- 2.59
365 cubic centimetres of wall, so about 730 grams in the finished piece and 820 grams to prepare. It fires to about 9.3 cm across.
A large serving bowl
A 28 cm diameter, 10 cm tall bowl with a 9 mm wall.
You enter
- Outside diameter
- 28 cm
- Height
- 10 cm
- Wall thickness
- 9 mm
- Wet clay density
- 1.95 g per cubic cm
- Fired clay density
- 2.15 g per cubic cm
- Linear shrinkage
- 8%
- Throwing and trimming loss
- 15%
You get
- Wet clay in the finished wall
- 2,624.42 g
- Wet clay to prepare
- 3,018.09 g
- Wet clay to prepare
- 3.02 kg
- Wet clay if the form were solid
- 12,007.17 g
- Weight of the fired piece
- 2,893.60 g
- Volume of clay in the wall
- 1,345.86 cu cm
- Total surface area of the shell
- 1,495.40 sq cm
- Fired outside diameter
- 25.76 cm
- Fired height
- 9.20 cm
- Capacity if the form were a closed cylinder
- 4.79 L
- How many times a solid volume guess would overstate the clay
- 4.58
Just over 1.1 kilograms of wall clay, so about 1.3 kilograms to weigh out. Large diameter forms are where the throwing loss grows.
A solid sculptural form
A 12 cm diameter, 20 cm tall form treated as solid.
You enter
- Outside diameter
- 12 cm
- Height
- 20 cm
- Wall thickness
- 60 mm
- Wet clay density
- 2 g per cubic cm
- Fired clay density
- 2.15 g per cubic cm
- Linear shrinkage
- 6%
- Throwing and trimming loss
- 5%
You get
- Wet clay in the finished wall
- 10,404.95 g
- Wet clay to prepare
- 10,925.20 g
- Wet clay to prepare
- 10.93 kg
- Wet clay if the form were solid
- 4,523.89 g
- Weight of the fired piece
- 11,185.33 g
- Volume of clay in the wall
- 5,202.48 cu cm
- Total surface area of the shell
- 867.08 sq cm
- Fired outside diameter
- 11.28 cm
- Fired height
- 18.80 cm
- Capacity if the form were a closed cylinder
- 1.88 L
- How many times a solid volume guess would overstate the clay
- 0.43
Setting the wall thickness to half the smallest dimension makes the model treat the form as solid, which needs about 9 kilograms. Solid forms should be hollowed or made in sections for firing, which is a manufacturer and kiln safety question rather than a quantity one.
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