Grading Seams – Sewing Bulky Seams Tutorial
Grading seams involves cutting the seam allowance at different widths so that when your project is pressed to the right side, it eliminates bulk and results in a flat seam that sits nicely. This sewing tutorial will show you how to grade seams, including basic seams, intersecting seams, and seams with multiple layers.
Are you having problems sewing bulky seams? Grading seams and grading seam allowance are especially important when you are sewing thicker fabrics in your Winter sewing patterns, and they will make your sewing projects look more professional. Reducing bulk by layering seams will give a smoother finish on the outside of your garments.
How Big is a Yard of Fabric (Quick Guide)
Grading seams means trimming seam allowances to different widths to reduce bulk and help seams lie flatter. Here is a quick summary or grading a seam:
- Sew the seam normally
- Trim one seam allowance narrower
- Layer additional seam allowances if needed
- Finish the seam edges
- Press the seam flat
What are Grading Seams?
Grading seams is a sewing term that refers to layering the seam allowance in order to reduce bulk in thick fabrics. Because it reduces bulk, it gives a professional look on the outside and a more comfortable fit for clothing.
When sewing, grading seams is only needed where you will be pressing the seam to one side or in areas, such as collars or cuffs, that will be turned right side out. It is not necessary for straight seams that will be pressed open.
How to Grade Seams (Step by Step)
Here are the step-by-step instructions for grading your seam allowance:
1. Sew the Seam
Start by stitching your seam as per the sewing pattern instructions. This seam had a seam allowance of ½ inch (12mm).
2. Trim to Grade the Seam
Use small scissors to grade the seam allowance by trimming one of the layers of seam 1/8 inch (3mm) narrower than the other. Where you have a curved seam line(eg necklines or armholes), grade first before clipping the curves.
In this example, I had 2 layers of fabric, so I left the outside seam allowance at ½ inch (12mm) and trimmed the other at 3/8 inch (1cm). Always be careful not to trim too close to the stitch line when you have fabrics that fray badly.
3. Finishing
As the seam allowance is now in layers, you will need to finish them separately. Use a seam finish that does not add bulk, such as using pinking shears.
4. Press the Seam Allowance
Once you have graded the seam, you can press it to one side. I always like to press so that the wider layer is on top and covers the narrower layers underneath.
How to Grade Seams with Multiple Layers
When grading seams where you have more than 2 layers, grade the seams to 3 different layers. You may need to grade a couple of layers to the same width, so you are not cutting right back to the seam allowance.
Grading Seams with Intersections
Where you have 2 seams that intersect, such as the underarm area, trim the ends of the seam into a point to reduce bulk. This way, when you press the seam open, there are not 4 layers at the intersection of the 2 seams.
Here you can see how it looks when the seam is graded at an intersection. This will sit much flatter in your final product.
What Does Layer Seam Mean?
Layering a seam is just another term for grading of the seam allowance. This means cutting the excess fabric at the seam in different layers in order to reduce bulk. This is important when using thicker fabrics for garments that you want to look professionally finished.
Grading Seams vs Trimming Seams
These sewing terms are related but different.
| Grading Seams | Trimming Seams |
|---|---|
| Seam allowances cut to different widths | All layers cut evenly |
| Reduces bulk gradually | Reduces overall seam allowance |
| Used on thick or layered seams | Used on many seam types |
| Creates flatter edges | Removes excess fabric |
Common Grading Seam Mistakes and Tips
| Common Mistake | Tip for Better Results |
|---|---|
| Trimming too close weakens the seam. | Leave enough seam allowance beside the stitching line. |
| All layers trimmed evenly still create bulk. | Grade each layer to different widths. |
| Skipping pressing leaves bulky seams. | Press carefully after grading. |
| Thick seam finishes add extra bulk. | Use low-bulk seam finishes. |
| Curves pucker after turning. | Grade first, then clip curves. |
| Intersections become stiff and thick. | Trim seam intersections into points. |
| Dull scissors chew the fabric edges. | Use sharp sewing scissors or duckbill scissors. |
| Heavy fabrics show seam ridges from the outside. | Grade seams gradually to smooth the layers. |
Grading Seams FAQs
Trimming a seam allowance is done through all layers. For example, if the instructions say to trim the seam to 1/4 inch then you will cut through both layers. Grading, by contrast, means layering each side of the seam in order to reduce bulk.
If you are grading your seam on the odd occasion, just use a small pair of scissors that are sharp and easy to control. For regular grading, you should use a pair of duckbill scissors. These scissors have an oversized curved bottom blade that is used for applique.
Because facings are curved, you will need to reduce the seam allowance in layered tiers in order to reduce bulk. Trim the first seam allowance layer to 1/8″ from the stitching line. Take care not to cut through the stitching. Then trim the second layer 1/8″ from the first layer.
When used in conjunction with sewing patterns, grading means to size up or down in order to get a complete set of sizes. For example your sample pattern may be a size 8 and you will use grading rules in order to get the larger and smaller sized patterns. This means you don’t have to start from scratch to make a pattern for each size.
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Grading Seams – In Conclusion
Grading seams is one of the simplest techniques for reducing seam bulk and improving the professional appearance of sewing projects. Whether you are sewing thick winter fabrics, collars, facings, or intersecting seams, grading helps garments sit flatter and feel more comfortable. Once mastered, grading seams becomes an essential finishing technique for creating smoother, cleaner sewing results.
If you are a beginner, here are some more popular articles to get you sewing.
- Clipping Corners and Curves
- How to Use a Sewing Machine
- Sewing Corners
- Sewing Curves
- Sewing 101 for Beginners
- French Seams
Author - Luisa Clare
Luisa Clare is the founder of Treasurie, a sewing and crochet education platform offering step-by-step tutorials and printable patterns. With over 15 years of experience in dressmaking, pattern design, crochet, and craft education, she specialises in teaching beginners through clear, easy-to-follow lessons. Her tutorials and patterns are used by home sewists and crocheters worldwide to build practical skills and confidence. Learn more about Luisa and Treasurie.
