UD5 Toolkit
Felting Shrink Calculator – Online Predict Wool Felted Size
Felting Shrink Calculator
Online Predict Wool Felted Size – Plan your felting projects with confidence
| Wool Type | Wet Felting | Machine Felting | Needle Felting | Avg. Shrink |
|---|---|---|---|---|
| Merino | 30–38% | 32–42% | 8–15% | ~30% |
| Corriedale | 25–33% | 28–38% | 7–13% | ~28% |
| Shetland | 22–30% | 25–35% | 6–12% | ~25% |
| Bluefaced Leicester | 20–28% | 22–32% | 6–11% | ~23% |
| Romney | 18–26% | 20–30% | 5–10% | ~21% |
| Alpaca | 12–22% | 15–26% | 4–9% | ~16% |
What is wool felting shrinkage?
Felting shrinkage is the reduction in size that occurs when wool fibers are exposed to moisture, heat, and agitation. The scales on wool fibers interlock and tighten, causing the fabric to shrink—typically 10–40% depending on wool type and felting method.
How is the felted size calculated?
The formula is: Felted Size = Original Size × (1 − Shrink Rate/100). For example, a 20 cm piece with 30% shrink rate becomes 20 × 0.7 = 14 cm. Area loss is calculated as 1 − (1 − rate)², so 30% linear shrink equals ~51% area loss.
Why do different wool types shrink differently?
Finer wools like Merino have more scales per inch and felt more readily, leading to higher shrinkage. Coarser wools like Romney have fewer scales and resist felting. Alpaca fiber has smoother scales, resulting in the least shrinkage among common felting wools.
Can I use this calculator for reverse planning?
Yes! Switch to "Felted → Original" mode. Enter your desired final size, and the calculator will tell you what size wool piece you need to start with. This is especially useful when you have a specific project dimension in mind.
What factors affect felting shrinkage?
Key factors include: water temperature (hotter = more shrink), agitation intensity, soap type, felting duration, wool type, and whether you use a washing machine or hand-felt. Even humidity and pH levels can influence the final result.
How accurate is this felting shrink calculator?
This calculator provides estimates based on typical shrinkage ranges. Actual results may vary by ±5% due to real-world variables like water temperature, agitation method, and individual wool batch characteristics. We recommend doing a small test swatch first.
What is the difference between wet felting and needle felting?
Wet felting uses water, soap, and friction, causing significant shrinkage (25–40%). Needle felting uses barbed needles to mechanically interlock fibers with minimal shrinkage (5–15%). Machine felting in a washing machine typically yields the highest shrinkage (30–45%).
How can I minimize unwanted shrinkage?
Use cooler water, minimal agitation, and monitor the felting process closely. For needle felting, shrinkage is already minimal. When wet felting, check your piece frequently and stop when you reach the desired size. Some crafters pre-shrink wool before starting a project.
Pro Tips for Accurate Felting
- Always test a swatch – Cut a 10×10 cm sample and felt it first to measure actual shrinkage before committing to your full project.
- Track your results – Keep notes on wool type, method, water temp, and shrinkage % for future reference.
- Shrinkage is often uneven – Length and width may shrink at slightly different rates. This calculator assumes uniform shrinkage.
- Consider the project type – 3D objects like bowls or hats may shrink differently than flat pieces due to gravity and shaping during felting.