Pattern Grading Calculator
Calculates new pattern measurements when grading a sewing pattern up or down between sizes. Use it when resizing a commercial pattern to fit a different size without redrawing every piece from scratch.
About this calculator
Pattern grading is the process of scaling a sewing pattern from one size to another by applying a consistent increment to each measurement. The core formula is: New Measurement = originalMeasurement + ((targetSize − originalSize) × gradingIncrement). The grading increment represents how much each measurement changes per size step — for example, a bust measurement might increase by 0.5 inches per size. Multiplying the size difference by this increment gives the total adjustment, which is added to (or subtracted from) the original measurement. The result is rounded to two decimal places for practical cutting accuracy. This method preserves the proportional relationships in the original pattern while producing a properly fitted new size.
How to use
Suppose a bodice side seam measures 14 inches at size 10, and you want to grade it to size 14 using a grading increment of 0.375 inches per size. Step 1: Find the size difference — 14 − 10 = 4 sizes. Step 2: Multiply by the increment — 4 × 0.375 = 1.5 inches total adjustment. Step 3: Add to original — 14 + 1.5 = 15.5 inches. The calculator rounds to two decimal places, giving a graded measurement of 15.50 inches for the size 14 pattern piece.
Frequently asked questions
What is a grading increment in sewing pattern grading?
A grading increment is the fixed amount a pattern measurement increases or decreases between consecutive sizes. It varies by measurement area — bust, waist, and hip increments are often different. Standard commercial patterns typically use increments between 0.25 and 0.5 inches per size. Knowing your increment lets you grade across multiple sizes in a single calculation rather than step-by-step.
How do I find the correct grading increment for my pattern?
Most commercial sewing patterns include a grading chart or size chart in their instructions that lists measurements per size. Subtract the measurement at one size from the next size up to find the increment for that area. Industry standards (like ASTM or ISO sizing) publish standard increments if your pattern doesn't specify them. For custom or indie patterns, the designer may state grading increments explicitly in the instructions.
When should I grade a sewing pattern instead of just choosing a larger size?
Grading is most useful when your measurements fall between two printed sizes, or when different body areas require different sizes — for example, a size 12 bust with a size 16 hip. It's also the right approach when you own a vintage or out-of-print pattern and need to fit it to modern measurements. Grading preserves the original design lines and ease allowances better than simply cutting a different size or slashing and spreading.