Pattern Grading Calculator
Determine how much to shift each grading point on a sewing pattern when adjusting from one size to another. Use it when resizing commercial patterns or custom blocks to match specific body measurements.
About this calculator
Pattern grading is the process of systematically increasing or decreasing a pattern to a different size while maintaining its proportions. The formula here is: Grade per Point = ((targetMeasurement + ease) − (originalSize + ease)) / gradingPoints. The ease values cancel algebraically (since both original and target include the same ease), simplifying to (targetMeasurement − originalSize) / gradingPoints. The result tells you how many inches (or centimeters) to move each grading point outward or inward on the pattern piece. Grading points are specific landmarks — typically side seams, shoulder seams, waist, and hip — distributed around the pattern. Dividing the total size difference equally across all grading points ensures smooth, proportional transitions between sizes rather than abrupt jumps at one location.
How to use
Example: original pattern size = 36-inch bust, target measurement = 40 inches, design ease = 2 inches (same for both), gradingPoints = 4 (two side seams × two layers). Step 1 — Compute numerator: (40 + 2) − (36 + 2) = 42 − 38 = 4 inches total difference. Step 2 — Divide by grading points: 4 / 4 = 1 inch per grading point. Step 3 — Move each of the 4 grading points outward by 1 inch. This distributes the 4-inch increase evenly, maintaining the original silhouette at the larger size.
Frequently asked questions
What is pattern grading and how is it different from resizing a pattern?
Pattern grading is a technical method of proportionally scaling each pattern piece to a different size by moving specific grading points by calculated amounts. Resizing broadly refers to any size change, which might include slashing and spreading or simple scaling. Grading preserves the original design lines and ease distribution, whereas simple scaling can distort details like pocket placement and collar shaping. Professional graders use grading rules — standardized increments per size step — to ensure consistency across a size range.
How many grading points should I use when distributing a size adjustment around a pattern?
The number of grading points depends on the garment area being graded. A bodice front might have 4–6 grading points (side seams, shoulder seams, and center front), while a skirt might use 4 (two side seams front and back). Using more grading points creates smoother, more gradual transitions and is preferred for fitted garments. For a simple A-line skirt or basic block, 4 grading points is typically sufficient. Always distribute adjustments to both front and back pieces equally to maintain symmetry.
How do I account for ease when grading a pattern to a new size?
Design ease — the extra room added for movement and style — should remain constant across sizes unless you are deliberately changing the fit. In the grading formula, ease appears in both the original and target terms, so it cancels out: the grade amount equals only the difference in body measurements. Wearing ease (minimum movement ease) may need to increase slightly for larger sizes to maintain comfort, particularly in sleeves and across the back. Always check industry ease standards for your garment type and adjust grading if the ease values differ between the original and target size.