Clay loses water as it dries and shrinks again as it is fired. Total shrinkage is typically 10–15% for stoneware and porcelain and 5–10% for earthenware. Measure your own clay with a test bar: draw a 10 cm line on wet clay and measure it after firing.
How to use the Clay Shrinkage Calculator
- I know the
- Length / diameter
- Width
- Height
- Total shrinkage
Results update as you type, and every field accepts the units shown in its menu.
How it works
Choose whether you know the wet size or the target fired size, enter the dimensions and the clay’s total shrinkage.
Tips
- Results are estimates meant for planning and fun – adjust the inputs to match your situation.
- Everything runs in your browser, so you can try as many variations as you like.
- Share the result link with friends so everyone sees the same numbers.
- For safety-related hobbies (hammocks, balloons, tents), follow the manufacturer’s limits.
Common mistakes to avoid
- Using default values when you know your own figures.
- Treating rough rules of thumb as exact.
- Forgetting to add breaks, travel or setup time.
Inputs explained
| Field | What to enter |
|---|---|
| I know the | Choose one: Wet (greenware) size, Fired size I want |
| Length / diameter | Units: cm, in, mm, m |
| Width | Units: cm, in, mm, m |
| Height | Units: cm, in, mm, m |
| Total shrinkage | In % |
Example values
How the main result changes when Length / diameter changes and everything else stays at the example values above:
| Length / diameter (cm) | Length (cm) |
|---|---|
| 7.5 | 6.6 |
| 11.25 | 9.9 |
| 15 | 13.2 |
| 18.75 | 16.5 |
| 22.5 | 19.8 |
| 30 | 26.4 |
Formula
Fired size = wet size × (1 − shrinkage)Wet size needed = fired size ÷ (1 − shrinkage)Shrinkage % = (wet length − fired length) ÷ wet length × 100Worked example
Inputs — I know the: Wet (greenware) size; Length / diameter: 15 cm; Width: 10 cm; Height: 12 cm; Total shrinkage: 12 %.
Results — Length = 13.2 cm; Width = 8.8 cm; Height = 10.56 cm; Volume change = -31.9 %.
Frequently asked questions
How much does clay shrink?
About 10–15% for most stoneware and porcelain from wet to fired, less for earthenware.
How do I measure clay shrinkage?
Make a test bar, mark 10 cm while wet, fire it and measure: 8.8 cm means 12% shrinkage.
Why does volume shrink more than length?
Shrinkage happens in all three dimensions, so 12% in length means about 32% less volume.
What formula does the Clay Shrinkage Calculator use?
Fired size = wet size × (1 − shrinkage).