Clay & Shrinkage

Clay Inventory Calculator

Calculate how many ceramic pieces you can make from your current clay stock, accounting for trimming waste, cracking losses, and kiln scrap.

Reviewed by ClayCalc Editorial · Updated

Total wet clay weight in stock.

Wet clay weight per finished piece before any waste.

Trimming, cracking, kiln losses. Typical: 10–20%.

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Results

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Enter your measurements above and click Calculate.

How Clay Inventory Is Calculated

This calculator tells you how many finished pieces you can make from your current clay stock, accounting for waste from trimming, cracking, and kiln losses.

Clay Per Piece (Including Waste)

Clay per piece = Piece weight ÷ (1 − Scrap rate)

At a 15% scrap rate, you need 588 g of clay to produce one 500 g piece — accounting for the clay lost to trimming and the percentage of pieces that won't survive to sale.

Total Pieces Possible

Pieces = floor(Clay on hand ÷ Clay per piece)

Estimated Fired Weight

The calculator estimates the fired weight by applying an average drying and firing shrinkage factor based on your form type:

  • Wheel throwing: ×0.86 (approx. 14% weight loss)
  • Handbuilding: ×0.83 (approx. 17% weight loss)
  • Slip casting: ×0.90 (approx. 10% weight loss)

Typical scrap rates: Slip casting 5–8% · Wheel throwing 10–18% · Handbuilding 15–25% · Student / learner 25–35%.

Method & review note

About this calculation

Uses measured dimensions or weights and a stated arithmetic model. Clay and forming method vary, so production decisions should use test pieces from the actual body and firing.

Reference: Digitalfire — Drying Shrinkage. See the editorial methodology for testing, precision and corrections.

Input handling: Values are sent to the ClayCalc server for this request and are not written to the application database.

Read the Clay Shrinkage Test

Frequently Asked Questions

Should I weigh my clay before or after wedging? expand_more
Weigh the ball of clay you put on the wheel, not the finished trimmed piece. The "average piece weight" in this calculator refers to the wet clay input weight, from which the finished piece will be shaped and trimmed. If you consistently use 500 g balls, enter 500 g.
How is scrap rate different from trimming weight? expand_more
Scrap rate covers all losses across the full process: clay trimmed off the wheel, cracked greenware, kiln accidents (explosions, crawled glaze, warped pieces), and pieces rejected at quality control. Trimming weight alone is typically 10–15% of the throwing weight; total scrap from throw-to-sale is usually 15–25% including firing losses.
Can I use this for a production order? expand_more
Yes. Enter your entire clay stock in the "clay on hand" field and the average piece weight for the form you're making. The result tells you whether you have enough clay to complete the order (accounting for scrap), or whether you need to order more clay before starting.
Why does fired weight differ from wet weight? expand_more
Clay loses significant weight during drying (water evaporates) and firing (organic matter burns off, chemical water is driven out). Stoneware typically loses 12–18% of its wet weight by the final fired state. The estimated fired weight shown is an approximation based on typical drying and firing shrinkage for your chosen form type.