Stretch percentage tells you how much a fabric can stretch compared to its original size. This helps you know if the fabric will work for a fitted stretch garment like a catsuit or leotard.
For example, if a fabric stretches from 4 inches to 6 inches, it has 50% stretch. That means it stretched 2 inches beyond its original 4 inches.
How to Test Stretch Percentage
- Cut a strip of fabric about 4 inches (10 cm) wide.
- Hold the fabric at 0 inches and 4 inches without stretching.
- Gently stretch it as far as it comfortably goes.
- Measure how far it stretches.
Use this simple formula:
Stretch % = (How Much It Stretched ÷ Original Length) × 100
Example: If 4 inches stretches to 6 inches, it stretched 2 inches. 2 ÷ 4 = 0.5 0.5 × 100 = 50% stretch.
Most Katkow patterns work best with four way stretch fabrics, and the direction with the most stretch should go horizontally around the body.
What Is Pattern Adjustment Ratio (P.A.R.)?
Once you know your stretch percentage, you can calculate your Pattern Adjustment Ratio, or P.A.R. This number helps you scale pattern measurements correctly when drafting or adjusting stretch garments.
When drafting stretch garments, you calculate two P.A.R. values: one for Width and one for Length.
P.A.R. works the same in inches or centimeters. The units cancel out, so use whichever measurement system you prefer.
You can use our free calculator here: Pattern Adjustment Ratio (P.A.R.) Calculator for Stretch Fabrics.
Testing stretch percentage first, then calculating your P.A.R., ensures your garment fits properly before you cut your final fabric.