Pottery Coil Building Height Calculator
Calculate coil count and clay weight to build a pottery vessel from coil diameter, wall thickness, and target height.
Useful for hand-building bowls and vases.
How Pottery Coil Building Height Is Calculated
Coil building is one of the oldest pottery techniques, dating back over 25,000 years. Each coil adds a predictable amount of height depending on its diameter (thickness) and the degree to which it is compressed during smoothing.
Core Formula
Height per coil:
Height_per_coil = Coil_Diameter × Compression_Factor
The compression factor accounts for how much the coil flattens when pressed onto the previous layer:
- Light smoothing: 0.85 (coil retains most of its round shape)
- Moderate smoothing: 0.70 (standard technique)
- Heavy smoothing: 0.55 (coil is fully blended into the wall)
Number of coils needed:
Coils_Needed = Target_Height / Height_per_coil
Clay per coil (grams):
Each coil is essentially a cylinder. The volume of clay is: Volume = π × (Coil_Radius)² × Coil_Length
Where Coil_Length is the circumference of the vessel at that layer: Coil_Length = π × Vessel_Diameter
Clay weight = Volume × Clay_Density (approximately 1.8 g/cm³ for wet stoneware)
Worked Example
Building a vessel 20 cm tall, 15 cm diameter, with 1.5 cm coils and moderate smoothing:
- Height per coil: 1.5 × 0.70 = 1.05 cm
- Coils needed: 20 / 1.05 = 19.05, round up to 20 coils
- Length per coil: π × 15 = 47.1 cm
- Volume per coil: π × (0.75)² × 47.1 = 83.3 cm³
- Weight per coil: 83.3 × 1.8 = 149.9 g
- Total clay: 20 × 149.9 = 2,998 g ≈ 3.0 kg
Shrinkage Note
Clay shrinks 10-15% during drying and firing. Add approximately 12% to your target height if you need a specific finished size. This calculator shows the wet-building dimensions.
Coil Thickness Reference
| Coil Diameter | Best For |
|---|---|
| 0.5 - 1.0 cm | Small decorative pieces |
| 1.0 - 1.5 cm | Standard bowls and cups |
| 1.5 - 2.5 cm | Medium vessels and vases |
| 2.5 - 4.0 cm | Large pots and planters |
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.