How clay weight estimates work
The calculator works backward from your desired fired dimensions to the wet dimensions using your shrinkage rate, then computes the geometric volume of the wet clay shell (walls + base). That volume is multiplied by clay density (approximately 1.8 g/cm³ for most wet clay bodies) to give an estimated weight.
Why results are estimates, not guarantees
Geometric calculations assume a perfect uniform shell. In practice:
- Throwing style — a tight base in a mug may be thicker or thinner than the specified base figure
- Trimming — significant clay is removed during trimming, reducing the finished weight
- Handle and attachment weight — handle clay is not included in most shape calculations
- Reclaim and floor scraps — clay lost to the floor, bat, or reclaim bucket
- Density variation — different clay bodies have different densities; groggy or open-body clays may be lighter
Use the waste percentage field to add a buffer for these losses. A 10–20% buffer is typical for experienced throwers; beginners may want 20–30%.
Adjusting clay density
Wet clay density typically ranges from about 1.7 to 1.9 g/cm³ depending on water content and clay body composition. The default value of 1.8 g/cm³ is a common mid-range figure. If your studio has a specific gravity measurement for your clay slop, you can use that as a guide to calibrate the estimate.
Planning a production run
Multiply the "with waste" weight by the number of pieces you plan to make to estimate total clay requirements for a studio session. Add a further 5–10% margin for unexpectedly thick pieces or pieces that get recycled during throwing.