Clay Shrinkage Calculator
Ensure tiles, mugs, and sculpture components finish at the right size by accounting for clay body shrinkage.
Most stoneware shrinks 10–15%, porcelain up to 16–20%.
Finished Dimensions
Length
8.8 units
Width
7.04 units
Height / thickness
0.88 units
How to Use This Calculator
Measure your wet piece
Record length, width, and height after forming but before drying. Use consistent units (inches, centimeters).
Determine shrinkage percent
Look up the clay body’s shrinkage from the manufacturer or measure a test tile—subtract fired size from wet size.
Plan your sizing
Use the calculated finished size to adjust molds, slab templates, or wheel-thrown walls so the final piece matches design specs.
Formula
Finished Size = Wet Size × (1 − Shrink%)
Shrinkage Ratio = 1 − Shrink% / 100
Scale Up Factor = 1 / Shrinkage Ratio
Example: Wet tile 10 in, shrinkage 12% → Finished = 10 × 0.88 = 8.8 in. Build wet pieces 1.136× your desired fired size.
Studio Tips
Shrinkage varies with clay body, water content, and firing temperature. Track your own averages for consistency.
- Make test tiles whenever you switch clay or firing schedules.
- Account for glaze thickness—it may add up to 1–2% shrinkage.
- Design molds/slabs larger by the scale-up factor to hit target dimensions.
- Dry pieces slowly and evenly to minimize warping during shrinkage.
Frequently Asked Questions
Does shrinkage happen during drying or firing?
Both. Clay shrinks as water evaporates and again during vitrification in the kiln. Manufacturers usually report total shrinkage.
Do glazes affect shrinkage?
Yes—glazes can add slight shrinkage or expansion. Test finished sizes with glaze to be precise.
How do I measure shrinkage percentage?
Make a test strip with markings (e.g., 10 cm). Measure wet, bisque, and fired lengths. Shrink% = (Wet − Fired) ÷ Wet × 100.
What if my pieces warp?
Warping changes finished dimensions unpredictably. Improve drying control, use supports, and refine clay body to maintain shape.