#18 How to Add a Size to a Pattern

Have you ever found a sewing pattern you love—only to realize it doesn’t include your size?

Before you give up or start searching for a different design, there’s a solution: grading the pattern up to your size using the existing size nest as your guide.

In this tutorial, I’ll walk you through a method for adding one size to a multi-sized sewing pattern. It’s a precise, hands-on approach that you can apply to nearly any pattern that includes multiple sizes. Whether you’re trying to expand your size range or adapt a favorite pattern to your current shape, this technique will give you the confidence and control to do it accurately.

What You’ll Learn in This Tutorial

• How to analyze the existing grading in your pattern

• Where to identify anchor points for size expansion

• How to measure and apply consistent grading increments

• How to accurately plot and draw the next size

We’ll be working with the Belle sewing pattern, but the method works with any nested pattern. You can also use this technique in reverse to reduce a pattern by one size.

Why Understanding Grading Matters

Most multi-sized sewing patterns are created using a specific grading rule—a consistent size increase between each layer of the pattern nest. When you understand how that system works, you can extend or contract a pattern by a full size while maintaining the designer’s proportions and styling.

However, not all grading rules are equal. Some patterns use different grading increments for smaller sizes and larger sizes. In the Belle pattern, for example, the increments between sizes 0–8 are smaller than those between sizes 8–16.

That’s why in this tutorial, I'm sizing up so I focus on the grading rule between the larger sizes—so I get a more proportional result for the size I need.

The Grading Process (Simplified)

Here’s an overview of the steps I walk through in the video:

1. Identify Key Anchor Points

Start by tracing the largest size available in the pattern. Then, locate the critical points along the seams and darts. These will guide where and how much the next size needs to expand.

2. Extend the Grade Lines

Using a ruler and pencil, extend lines from each anchor point in the same direction and distance as the previous size increments. These extensions become the path for plotting your new size.

3. Measure the Increments

Measure the distance between the nested sizes—at each key point. Use these consistent measurements (e.g., ⅛", ¼", or ⅜") to plot the next size point along the grade lines.

4. Connect the Dots

Once all the new size points are marked, use a ruler or curved tool to redraw the seam and cutting lines, following the shape of the previous size as a guide.

5. Mark Internal Details

Don’t forget to update notches, pleats, darts, and internal markings. These should follow the same spacing pattern as the external seams.

Tip: Precision matters. The more accurate your plot points and lines, the more true-to-fit your final pattern will be.

When Should You Use This Method?

• When a favorite pattern doesn’t include your current size

• When you want to make garments for someone outside the size range

• When you're adapting vintage or discontinued patterns

• When you want to scale a pattern up or down consistently

This method is especially helpful for sewists who prefer structured, repeatable processes over trial-and-error.

Resources to Support You

📥 Perfect Fit Guide — A free, step-by-step PDF guide that outlines the six core stages of fitting success.

🧵 Belle Sewing Pattern — Follow along with the same pattern used in the video.

🎓 Fitting Essentials Course — Learn a complete, professional system for adjusting patterns to your exact body shape.

Final Thoughts

Grading a pattern up one size may seem intimidating at first, but once you understand the logic behind pattern nests, it becomes a powerful tool in your sewing skill set. With this method, you’re no longer limited by size charts—you’re in full control.

Whether you’re adjusting a tried-and-true favorite or adapting a new style, this method gives you the flexibility to create a pattern in your size.

Next week, I’m going to share an inside look at how I prepare the Belle sewing pattern for fitting and what my initial pattern adjustments look like so that I can fit my pattern before I sew. I hope you’ll follow along with me using your own pattern.

I'll chat with you soon!
Alexandra