How to Sew French Seams

Haven’t sewn French seams before? You might be wondering:
What is a French seam? A French seam is a seam finish that makes a narrow seam that fully encloses the seam allowance in the seam.
Why use a French seam? It’s a great seam to use on woven fabrics that are sheer, delicate, or prone to fraying. It’s subtle, unlike a serged seam.
Can you sew a French seam on a curve? Yes! Though you will find that the narrower your finished seam is the less it will pull on the curve and that the softer your curve is the easier it is to sew the French seam.
How wide is a French seam allowance? A French seam is sewn in two steps and involves trimming of the seam allowance so you can start with whatever seam allowance you want and finish with a French seam of whatever size you want. A common combination is a 5/8″ total seam allowance with a finished seam width of 1/4″
How can I tell what my finished seam allowance will be? The finished seam allowance of a
French seam is the width of the first seam, plus the width of the second seam, plus a little bit to account for the turn of the cloth. You will generally find that if you sew your first and second seams each at 1/4″ your finish seam allowance will be 5/8″ (1/4″ + 1/4″ + 1/8″ turn of the cloth = 5/8″). Hint: Before starting to sew your French seam, mark the finished seam allowance at the top and bottom of your seam.

How do I sew a French seam? To sew a French seam, you start by sewing your fabric WRONG sides together. This is opposite from what you do for most garment construction, so make sure you override habit and sew WRONG sides together! Your pattern instructions should tell you what width to sew.

Press the seam allowance open. This “sets the seam” and makes it easier to get an accurate press when you press it to the side in the next step.

Press the seam allowance to one side.

Trim your seam allowance. Your pattern should tell you what width to trim, though 1/8″ is fairly standard.

Turn your project inside out so the fabric is now right sides together and sew your seam again.

Press the seam flat. That’s it!

Funny story time: In college I worked in our theatre’s costume shop. I had designed the costumes for a Senior’s thesis performance and one of the pieces was a kimono with a 10 foot train sewn out of a polyester chiffon. I had just sewn the last giant seam only to discover that I had sewn it wrong sides together and I was just about in tears at the idea of having to rip it out. My professor said “why don’t you just turn it into a French seam?” I didn’t even know what a French seam was at the time and it was a revelation and a godsend to learn about it right then since it meant that I didn’t have to rip that horrible polyester chiffon! Moral of the story: if you accidentally sew a seam wrong sides together, you can turn it into a French seam to save yourself from seam ripping!

Do you love French seams? What’s your favorite application for them?

Comments 3

  1. I haven’t thought about french seams for a long time. I remember my mom sewing them when I was young. I wonder how it would work in a quilt. I hate ripping out seams.

    1. Post

      It’s probably going to be fairly difficult to use in a quilt since the two seams and turn of the cloth have to equal your seam allowance. Most quilts use a 1/4″ seam allowance so you’ll have to sew less than 1/8″ seams to make a french seam will only a 1/4″ total seam allowance!

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