How To: Calculate Fabric Shrinkage In 3 Easy Steps

What Is Fabric Shrinkage?

Fabric shrinkage refers to any change in a fabric’s length and/or width after washing or dry cleaning. The shrinkage rate usually remains consistent whether you use a home washer, commercial laundry, or a dry-cleaning process. This matters greatly to ready-made garment suppliers because dimensional changes can affect overall fit and product quality.

Why Does Fabric Shrink?
• Material Quality: Lower-quality or unstable fibers are more prone to shrinkage.
• Manufacturing Tension: Fibers often get stretched during production; exposure to heat or moisture lets them relax, causing contraction.

In today’s competitive market, buyers expect minimal shrinkage at a low price. Consequently, manufacturers and suppliers strive to reduce shrinkage through better raw materials, controlled production, and advanced finishing techniques.

Fabric Shrinkage in the Garment Wash & Garment Dye Industries

Garment Wash: This process typically uses laundering techniques—often at elevated temperatures or with specialty washing agents—to soften the fabric or achieve a particular finish. Depending on the fiber type, this procedure can induce an additional 3–5% shrinkage if the fabric has not been preshrunk.

Garment Dye: In this method, garments are dyed after they are sewn, exposing them to chemical dyes, heat, and mechanical agitation. Natural fibers can experience up to 5–7% shrinkage if they haven’t been stabilized beforehand. This process also requires consistent monitoring of temperature and dye formulations to minimize undesired dimensional changes.

Common Natural Fiber Fabrics & Their Shrinkage

Types of Shrinkage

Fabric shrinkage can be categorized based on dimensional changes:

• Expansion (rare): Fabric grows in one or more directions.
• Contraction (common): Fabric shortens in length and/or width.

Natural fibers like cotton often continue to shrink after each wash, known as progressive shrinkage. In contrast, synthetic fibers typically shrink less due to their thermoplastic structure, though they may exhibit minor changes under high heat or mechanical stress.

Shrinkage of Natural vs. Synthetic Fibers

Natural Fibers (e.g., cotton, linen, wool, rayon):

• Higher water absorption leads to greater shrinkage potential.
• Progressive shrinkage with multiple washes.

Synthetic Fibers (e.g., polyester, nylon):

• Thermoplastic structure offers better dimensional stability.
• Generally lower shrinkage (often under 2%).

Residual Shrinkage can occur if tensions from manufacturing aren’t fully removed. Wet or heated conditions release these tensions, causing further fabric contraction over time.

How to Shrink Fabric Deliberately

If a garment is too large, washing it in hot water and tumble-drying on high often induces shrinkage. However, exact control can be tricky, as different fibers respond differently. Always test a small swatch to avoid unwanted results.

Fabric Shrinkage Control

Controlling shrinkage is essential for manufacturers and garment producers. Key strategies:

• Proper Manufacturing: Minimize yarn tension; choose higher-grade fibers.
• Finishing & Preshrinking: Heat-setting (synthetics), sanforizing (cotton), or resin/softener treatments.
• Moisture Management: High humidity can increase shrinkage; control environmental factors.
• Thermoplasticity: Use steam/heat to stretch the fiber, then cool to lock in shape.

Material Shrinkage Calculation

Shrinkage depends on:

• Fiber Composition (cotton vs. polyester vs. viscose, etc.)
• Fabric Structure (loose vs. tight weave/knit)
• Processing Tension (how much yarn is stretched)
• Finishing Treatments (heat-setting, resin finishes, etc.)
• Temperature & Mechanical Action (hot water, tumble-drying, agitation)

Methods for Calculating Fabric Shrinkage

Several standardized test methods exist:

• AATCC Test Method 135
• AATCC Test Method 150
• ISO 6330
• CAN/CGSB 58

These methods typically involve multiple wash-and-dry cycles, measuring the fabric before and after each cycle. A shrinkage rate under 2–3% is usually acceptable to consumers; over 3% often causes dissatisfaction.

Fabric Shrinkage Formula

Follow these three steps to calculate your fabric’s shrinkage percentage:

Step 1

Cut an 18" x 18" fabric sample and mark it clearly with a fabric marker, at least 2" from the selvage.

Before Wash Measurements:
Lengthwise = 18"
Widthwise = 18"

Step 2

Wash and dry the fabric sample following your standard procedure. Then measure again:

After Wash Measurements:
Lengthwise = 17"
Widthwise = 15"

Step 3: Apply the Formula

Shrinkage % (Lengthwise) = [ (Original Length – Final Length ) ÷ Original Length ] × 100
Shrinkage % (Widthwise) = [ (Original Width – Final Width ) ÷ Original Width ] × 100

Example
• Lengthwise: [(18 – 17) ÷ 18] × 100 = 5.55% ≈ 6%
• Widthwise: [(18 – 15) ÷ 18] × 100 = 16.66% ≈ 17%

If the final measurement is larger than the original, you would get a negative result, indicating expansion (less common).

Fabric Shrinkage Rates

Shrinkage can vary widely depending on fiber type, fabric structure, and finishing. Anything under 2–3% is generally acceptable. Over 3% often leads to customer dissatisfaction, potential returns, or additional garment alterations.

Fabric Shrinkage Questions (FAQs)

1. What Patterns Need Shrinkage Applied?

Any pattern using natural fibers—cotton, linen, silk, denim, corduroy, flannels, etc.— requires shrinkage allowances. These fibers are more susceptible to dimensional changes than synthetics.

2. What Is Selvedge (Selvage)?

It’s the tightly woven edge of the fabric that prevents unraveling. The “usable width” excludes this edge to avoid distortion or inconsistent seams.

3. Which Washing Process Shrinks Fabric?

Any wet washing or chemical process, including garment washes or dyeing, can cause shrinkage. Always test before large-scale production.

4. Which File Format Should I Upload for Shrinkage Adjustments?

You can upload Gerber ZIP files or DXF/AAMA files for digital pattern adjustments.

5. What If Shrinkage Exceeds 3%?

Many brands consider anything above 3% unacceptable. Additional preshrinking treatments or alternate finishing processes may be necessary to meet consumer expectations.

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