About the Clay Shrinkage Calculator
Clay shrinks in two stages between the wheel or slab and the finished piece: first as water leaves the clay during drying (wet to bone-dry), then again as the clay body vitrifies in the kiln (bone-dry to fired). This calculator uses length measurements from those three stages to find each shrinkage percentage, plus the wet size you need to build to hit a target fired dimension.
The formula
Shrinkage between any two stages is calculated the same way:
Shrinkage % = (Starting length − Ending length) ÷ Starting length × 100
Applying this formula stage by stage gives wet-to-dry shrinkage, dry-to-fired (firing) shrinkage, and total wet-to-fired shrinkage. Because the result is a percentage, any consistent length unit works — inches, centimeters, or millimeters — as long as you use the same unit for every measurement in one calculation.
Sizing a piece for a target fired size
To finish at a specific size, work backward from the total shrinkage percentage: Wet size = Desired fired size ÷ (1 − Total shrinkage ÷ 100). For example, a clay body with 12% total shrinkage and a 150 mm target fired height needs to be built to about 170.5 mm while wet.
Measuring shrinkage yourself
- Roll out a flat test bar and mark two points a fixed distance apart (10 cm is a common standard) while the clay is still wet.
- Measure the same span again once the bar is bone-dry, and a third time after it has been fired to your target temperature.
- Different clay bodies — and even different batches of the same clay — can shrink at slightly different rates, so always test the specific clay and firing schedule you plan to use.
Frequently Asked Questions
How do I calculate clay shrinkage percentage?
What is a normal shrinkage rate for clay?
How do I size a piece so it comes out the right size after firing?
Does the unit of measurement matter?
Common Tip Percentages
| Service | Typical Tip Range | Notes |
|---|---|---|
| Restaurant (sit-down) | 15–20% | 20%+ for exceptional service |
| Food delivery | 10–20% | Consider extra for long distances |
| Taxi / rideshare | 10–20% | More for assistance with luggage |
| Hotel housekeeping | $2–5/night | Leave daily, not just at checkout |
| Barber / hair salon | 15–20% | On pre-discount total |
| Pizza delivery | 10–15% or $3–5 minimum | Higher in bad weather |
General Household Budget Ratios (50/30/20 Rule)
| Category | % of Net Income | Examples |
|---|---|---|
| Needs | 50% | Rent, groceries, utilities, insurance |
| Wants | 30% | Dining out, entertainment, hobbies |
| Savings / Debt | 20% | Emergency fund, retirement, extra payments |
Common Measurement Conversions for Everyday Use
| Quantity | US / Imperial | Metric Equivalent |
|---|---|---|
| 1 cup | 8 fl oz | 237 mL |
| 1 pint | 16 fl oz | 473 mL |
| 1 quart | 32 fl oz | 946 mL |
| 1 gallon | 128 fl oz | 3.785 L |
| 1 lb | 16 oz | 453.6 g |
| 1 ft | 12 in | 30.48 cm |