Grading Calculator — Grade Patterns Between Sizes

Pattern grading is the process of proportionally increasing or decreasing a pattern to create different sizes. Each edge of the pattern moves by a calculated amount, maintaining the overall shape and proportions.

On the standard Big-4 / Misses grade (Simplicity, Vogue, Butterick, McCall’s) the grade is not uniform — it widens with size. Between the smallest sizes (4–10) the bust and hip grow about 2.5 cm (1 inch) per size; from size 10 to 12 about 3.8 cm (1½ inches); and from size 12 upward about 5 cm (2 inches) per size. The waist grades a little less through the mid-range and widens to about 5 cm (2 inches) per size from size 14 up. This calculator reads the exact Big-4 body chart (for example sizes 12/14/16 measure 34/36/38 inch bust, 26½/28/30 inch waist and 36/38/40 inch hip), so the change it reports matches the chart for the specific sizes you enter.

You can grade 1–2 sizes with reasonable accuracy. Beyond 2 sizes, proportions change significantly and it is better to use a pattern drafted for the target size range. Grading 3+ sizes can affect armhole shape, shoulder slope, and dart placement.

Grading moves all pattern edges proportionally. It is different from making a targeted adjustment (like a bust or hip adjustment) which changes only one area. Grading changes the entire pattern uniformly.