How to Sew a French Seam {With Video}

Learning to sew the best seam finishes for your garments is essential to ensure their overall longevity and quality, and in our humble opinion, the French seam is the most important finish to master. French seams are one of our favourite finishes because they are durable, work for a wide variety of fabrics, and give our garments that high-end couture look. In this tutorial, we’ll show you how to sew French seams and give you tips that will help you to French seam curves, darts and armholes. You are bound to be dazzled by their simplicity and sophistication!

What is a French Seam

A French seam is a strong and elegant enclosed seam finish where the seam allowance is folded and sewn twice to completely conceal the raw edge of the fabric. Because the construction of a French seam uses two rows of stitches instead of just one, they are more resistant and stable than a regular seam, and they keep the raw edge of the fabric from fraying. For these reasons, French seams are ideal for delicate fabrics like silk chiffon, crepe de chine, satin and viscose. They also work well for a wide variety of light to mid-weight wovens, such as cotton shirtings and linen. Since their construction creates seams that are 4 layers thick, we don’t recommend them for thick or heavyweight fabrics (for heavier duty seams we recommend serged seams or flat fell seams).

To help you visualize a French seam, imagine your hands are the seam allowance, the palm of your hands are the seam line, and your fingertips are the edge of the fabric. Make a tight heart shape with your hands curling your fingers towards the palms. As you can see, the tips of your fingers (or the raw edge of the fabric) are completely enclosed by your hands. A clean, enclosed seam is a thing of beauty!

French seam, analogy with hands on heart shape | Closet Core Patterns — Hands shaped as a heart, an analogy for French seams

Hands shaped as a heart, an analogy for French seams

This clean finish is a great alternative if you don't have a serger, or if the seam will be visible in the finished garment. We love #prettyguts around here, and there is no better way to make the inside of your garment just as beautiful as the outside!

Where to Use French Seams

French seams can be used to finish most seams. However, due to the nature of their construction, there may be times where it is not possible to fully French every single seam in a garment. Note that French seams are easiest to install on relatively straight seams; for this reason, they are ideal for side seams and inseams. With that said, in this tutorial we will cover the following:

How to sew traditional French seams
How to sew a French seamed dart
How to French seam an armscye
How to French seam curves

How to Sew a French Seam

To start, verify the seam allowance of your pattern. French seams work best with 5/8” (16 mm) seams, but they can also be achieved with a 1/2” (12 mm) seam. If your pattern only has a 3/8” (10 mm) seam allowance (which is typical in European and “industrial/commercial” patterns). you’ll need to add an additional 1/4” in order for this finish to work.

The following tutorial assumes your total seam allowance is 5/8” (16 mm) wide.

Pin your pattern pieces with the wrong sides together. Sew your first line of stitching at 3/8” (10mm). Trim the seam allowance in half to avoid catching the raw edge in the second pass of stitching. If you have one, try trimming this seam with a rotary cutter - it is much faster!

Press the seam to the side.

Now fold along the seam to bring the right sides together and press.

French seam. Fold along the seam. | Closet Core Patterns — Fold along the seam

Back at your machine, stitch the length of the seam at 1/4" (6 mm). Your stitch line should completely enclose the raw edge of the fabric.

French seam. Second pass of stitches. | Closet Core Patterns — Stitch the length of the seam.

Press the French seam to the front or back of the garment as indicated by the pattern. Start pressing on the wrong side, and repeat on the right side if necessary for a crisp seam.

French Seams Video Tutorial

How to French Seam a Dart

Start by tracing the legs of the dart on the right side of the fabric, then trace an inner dart 1/4” (6 mm) inside the original. Fold the dart.

Sew along the inner dart line, and trim the dart down to slightly more than 1/8” (3 mm). Press to the side over a tailor's ham.

Bring right sides together and fold the dart over the seam you created.

Back at your machine, stitch the length of the original dart at 1/4" (6 mm). Your stitch line should completely enclose the raw edge of the fabric.

Press the French seam dart to the side as indicated by the pattern instructions

How to French Seam a Sleeve

It is possible to french seam armscye or armhole before or after the side seam is sewn. This method works best for sleeves that have a minimal amount of ease - if the sleeve cap is too gathered, it can be difficult to French seam beautifully. In this case, we recommend serging or binding the seam with bias.

To start, gather along the sleeve cap with basting stitches if directed by the pattern instructions.

Wrong sides together, sew the sleeve to the bodice using a 3/8” (10 mm) seam allowance.

Trim the seam.

Just like the instructions for the French seam above, fold it together along the seam edge with right sides together.

Stitch once again at 1/4", and press the seam towards the sleeve.

How to French Seam Curves

While French seams work best for straight-ish seams, it is possible to French seam curved seams as well. Sew your first line of stitching at 3/8" with wrong sides together, just like a typical French seam. After you trim the seam allowance down, clip to but not through the seam allowance - this will allow the fabric to turn smoothly. Proceed to sew your second line of stitching to enclose the raw edge, just like you would with any other seam.

Be sure to use your iron, a tailor's ham, and lots of steam to help control the fabric .