Advanced8 min read
Pattern Grading Explained
What is Pattern Grading?
Grading is the process of scaling a base-size pattern up or down to create a full size range. It's not simply enlarging or shrinking — each measurement point moves by a different amount based on body proportions.
How Our Grading Works
Our grading applies a fixed rule table — the BOP size table — instead of scaling the whole pattern by one factor:
•Cross-grain growth: Width increases are distributed across the pattern piece (e.g., bust width splits between front and back panels)
•Length-grain growth: Vertical measurements grow by their own step per size, not by the same ratio as width
•Curve preservation: Armholes, necklines, and crotch curves are recalculated — not just scaled — for each size
•Dart adjustment: Dart depth and position shift with bust point changes across sizes
This is why a size 5XL pattern isn't a stretched-out small — each point moves by its own amount.
Grading Between Sizes
If your measurements fall between two sizes, you can blend:
1**Trace the larger size** for the area where you're bigger (e.g., hips)
2**Blend to the smaller size** where you're smaller (e.g., waist)
3**Draw a smooth line** connecting the two sizes at the transition point
4**Check the total measurement** of the blended piece against your body
💡 Note: Our patterns include all sizes in one file, making it easy to trace a custom blend between sizes.
💡 Tip: If you need to grade between sizes at the bust but not the hips (or vice versa), use the seam lines as your blending points — they create natural transition zones.