Pottery Shrinkage Calculator

Master ceramic sizing with precise shrinkage compensation. Calculate exact starting dimensions to achieve your desired finished size, accounting for both drying and firing shrinkage.

Calculate Shrinkage NowFree • Professional Formula • Instant Results

Clay Shrinkage Compensation Formula

The professional formula for perfect ceramic sizing:

Wet Size = Desired Size ÷ (1 - Total Shrinkage%)

Common Shrinkage Rates:

  • • Earthenware: 5-8%
  • • Stoneware: 8-12%
  • • Porcelain: 12-16%
  • • High-fire clays: 10-14%

Example Calculation:

Want: 4" bowl
Clay: 10% shrinkage
Make: 4 ÷ 0.90 = 4.44" wet

Understanding Clay Shrinkage Types

1
Drying Shrinkage

As clay loses water content

Typical Rates:

  • • Earthenware: 2-4%
  • • Stoneware: 3-5%
  • • Porcelain: 4-6%

Factors Affecting:

  • • Clay body composition
  • • Original moisture content
  • • Drying environment
  • • Piece thickness

2
Firing Shrinkage

During the firing process

Typical Rates:

  • • Bisque firing: 3-5%
  • • Glaze firing: 1-3%
  • • High-fire: 5-8%

Factors Affecting:

  • • Firing temperature
  • • Clay maturation point
  • • Firing schedule
  • • Kiln atmosphere

Shrinkage Rates by Clay Type

Earthenware

Cone 04-06

Drying:3-4%
Firing:3-5%
Total:6-9%

Terra cotta, red clay

Low-fire Stoneware

Cone 6-8

Drying:4-5%
Firing:4-6%
Total:8-11%

B-Clay, commercial bodies

High-fire Stoneware

Cone 10-12

Drying:4-6%
Firing:6-8%
Total:10-14%

Reduction stoneware

Porcelain

Cone 8-12

Drying:5-6%
Firing:7-10%
Total:12-16%

High-fire porcelain

Real-World Shrinkage Examples

Dinner Plate

Stoneware (10%)

Desired Size:

10"

Make Wet Size:

11.11"

Standard dinner plate size

Coffee Mug

Earthenware (7%)

Desired Size:

3.5" dia, 4" tall

Make Wet Size:

3.76" × 4.3"

12oz capacity when finished

Decorative Bowl

Porcelain (14%)

Desired Size:

8" dia, 3" deep

Make Wet Size:

9.3" × 3.49"

High shrinkage porcelain

Flower Pot

Stoneware (9%)

Desired Size:

6" dia, 6" tall

Make Wet Size:

6.59" × 6.59"

Drainage hole pre-shrinkage

Tile (4" square)

Low-fire (6%)

Desired Size:

4" × 4"

Make Wet Size:

4.26" × 4.26"

Account for warping

Vase

Stoneware (11%)

Desired Size:

5" dia, 10" tall

Make Wet Size:

5.62" × 11.24"

Tall pieces need extra support

Professional Shrinkage Tips

Testing Your Clay

  • Make test tiles to measure actual shrinkage
  • Test each new clay body separately
  • Account for your specific firing schedule
  • Keep detailed records for future reference

Minimizing Issues

  • Ensure even wall thickness
  • Slow, even drying prevents cracking
  • Consider clay memory and stress
  • Plan for slight variations in final size

Complete Pottery Toolkit

Master all aspects of pottery creation with our professional calculators

Firing Cost CalculatorGlaze CalculatorComplete Shrinkage Guide