How Apparel Size Grading Works Across Sizes.
Pattern size grading scales a base size pattern (typically Medium) proportionally up to 3XL and down to XS using precise technical grade rules.
General industry knowledge • Reviewed by Fenalt editorial team
Size grading is selective differential mathematical scaling - expanding circumference and length while preserving collar and sleeve ergonomics.
In industrial clothing production, factories do not draft brand-new patterns from scratch for every individual size. Instead, pattern makers perfect a single base size pattern and apply technical grade rules in CAD software to generate the full size run. Understanding how grade rules function ensures consistent brand fit across all retail sizes.
Grading Architecture
6 Principles of Apparel Size Grading
1. Base Sample Size Calibration (Medium/Large)
Pattern makers create and physically test a single master base size pattern (typically Medium for unisex/menswear). Once the base fit is signed off, all smaller and larger sizes are derived from this approved master.
2. Grade Rules (Differential Increments)
A grade rule specifies the precise numerical increase or decrease (+/- cm or inches) applied to each point of measure per size step (for example, +4.0cm circumference increase per size for chest width).
3. Non-Proportional & Selective Scaling
Anatomical scaling is non-linear. Collar openings, pocket dimensions, zipper lengths, and ribbing heights do not scale 1:1 with chest expansion. Grade rules hold specific details semi-static to prevent distortion.
4. CAD Computerized Vector Grading & Nesting
Modern pattern makers enter grade rule tables into garment CAD software (Lectra, Optitex, Gerber), generating a nested size stack (XS through 3XL) with perfect CAD seam alignment.
5. Size Set Sample Validation
For full-collection launches, brands request size set samples (e.g. Small, Large, 2XL) to verify that graded patterns fit real bodies comfortably at the extremes of the size range.
6. Alpha vs Numeric Size System Mapping
Grading accounts for sizing systems: Alpha grading uses letter ranges (XS, S, M, L, XL, 2XL), while Numeric grading uses exact inch/cm waist or chest dimensions (30, 32, 34, 36, 38).
Industrial Benchmarks
Typical Grade Rule Increments for Tops
Chest / Bust Circumference
Primary volume expansion driver.
Total Body Length (HPS)
Vertical length scales slower than chest width.
Across Shoulder Width
Shoulder slope requires proportional armhole pitch adjustments.
Sleeve Length (From CB)
Accounts for arm length and shoulder seam widening.
Neck Opening Width
Neck opening increases strictly controlled to prevent collar gaping.
Questions
Frequently Asked Questions
Can I just enlarge a Medium tech pack by 10% to create a Large size?
No! Uniform percentage scaling causes serious fit distortions. A 10% enlargement increases neck openings, pocket sizes, and zipper lengths excessively. Proper technical size grading applies selective differential increments (e.g. +4cm chest, but only +0.5cm neck opening).
What is a nested pattern in apparel CAD?
A nested pattern is a visual digital display in garment CAD software showing all size patterns (XS through 3XL) stacked on top of one another aligned by a central reference point (like High Point Shoulder), allowing pattern makers to inspect smooth grading transitions.
What is a Size Set Sample?
A Size Set Sample involves producing physical samples across the entire size run (e.g. Small, Large, 2XL) to test graded patterns on live models before authorising full bulk cutting.
What happens if size grading is done incorrectly?
Incorrect size grading leads to fitting failures in outer sizes - such as Small garments with oversized collars or 2XL hoodies with tight armholes. Verifying grade rules in your tech pack prevents customer return issues.
What is the standard base size for streetwear collections?
Streetwear collections typically use Medium (or Large for oversized streetwear fits) as the base fitting size. All pattern revisions are perfected on the base size before applying CAD size grading.
Does Fenalt provide pattern size grading services?
Yes. Fenalt's technical pattern team in Dhaka handles complete CAD pattern grading from base size spec sheets, generating DXF files and marker layouts for micro-factory production.
Precision pattern size grading
Fenalt's Dhaka CAD pattern team executes technical size grading from your base specs for seamless bulk production.
Submit Your Project