Start with a wet test bar
Make a small bar from the clay you use in the studio. Add two clear marks exactly 100 mm apart while wet. Measure the marks—not the ends of the bar.
THE POTTERY STUDIO · STAGING PREVIEW
A little shrinkage.
A better-fitting piece.
Know how big to make it before the kiln. Measure your clay’s shrinkage, then work backwards from the finished size you want.
YOUR STUDIO NOTES
Start with wet clay at
170.45 mm
to finish at 150 mm after firing.
12%Total linear shrinkage
1.1364×Starting-size multiplier
The calculation150 ÷ (1 − 12 / 100) = 170.45 mm
An estimate, not a fit guarantee. Clay body, forming direction, moisture, and firing conditions can change shrinkage. Test your actual clay and firing schedule.
✓ Your measurements, not a generic clay preset✓ No signup✓ Calculated in your browser
MEASURE ONCE. MAKE WITH CONFIDENCE.
How to test your clay’s shrinkage
A simple test bar gives you a more useful starting point than guessing a percentage from the clay’s name.
Follow your usual process
Dry the bar fully, then put it through your normal firing sequence to the final firing. Label the clay and record the cone and schedule so the test stays useful.
Check the same two marks
After the bar has cooled, measure between the same marks. Enter the wet and fired lengths above. Repeat with several bars to check consistency.
A 12% shrinkage rate does not mean “add 12%.” A 100 mm fired piece needs about 113.64 mm of wet clay at 12% shrinkage. Divide the target by 0.88 instead of multiplying by 1.12.
Test-bar reference: Digitalfire’s Shrinkage/Absorption Test (SHAB). This calculator uses wet-to-final-fired measurements for total linear shrinkage.
A few things worth knowing
What formula does the calculator use?
Total shrinkage (%) = (wet length − fired length) ÷ wet length × 100. Required wet size = desired fired size ÷ (1 − shrinkage ÷ 100). All lengths in each calculation must use the same unit. Results are rounded to two decimal places; the calculation uses unrounded values.
Is firing shrinkage the same as total shrinkage?
No. A dry-to-fired rate covers firing only. Wet-to-fired shrinkage includes drying and firing, which is what you need to size a wet piece. Do not simply add drying and firing percentages: their starting lengths are different.
Will this work for lids, mugs, and plates?
Use it to estimate a linear dimension such as a diameter or height. For fitted parts, test the actual form and allow suitable clearance; glaze thickness, distortion, and different forming directions can affect the fit. It does not calculate volume, clay weight, or glaze fit.
What if my fired bar is bigger than my wet bar?
This pilot handles shrinkage from 0% up to, but not including, 100%. If the fired length is larger, check the units and measuring marks. Expansion or bloating needs separate investigation rather than being treated as ordinary shrinkage.
FROM THE STUDIO NOTEBOOK
Go a little deeper
Measure consistently, choose the right percentage, and bring your result back to the calculator.
How to Test Clay Shrinkage in Your Studio
A practical studio method for measuring wet-to-dry and wet-to-fired clay shrinkage with marked test bars.
Drying vs. Firing Shrinkage: What the Percentages Mean
Understand the different starting points behind drying, firing and total clay shrinkage—and size wet work correctly.