Tutorial - Flat-felled seam

I’ve seen many flat-felled seam tutorials around the web, but sadly not one of them mimics industrial flat-felled seam.
When you look at the flat-felled seams on your store bought jeans you see two rows of stitches on both right and left side; cutting edges have been nicely tucked between two details on the outside and on the inside and the back center is right between those two rows of stitches.
And here is how you can do same looking flat-felled seam at home on your commercial sewing machine.
Step 1: Adding seam allowance before cutting
First you need to figure out how wide you want your flat-felled seam to be and how wide apart the two rows of stitches are going to be. I figured I will mimic the inseam on my favourite pair of jeans where the stitch rows are about 0,7 cm apart.
So you will multiply the width of your two seam rows by two.
I got 1,4 cm and decided to add 1,5 cm of seam allowance. (Really, 1 mm is not that big of a loss)

Step 2: Cutting and ironing
Now that you have added the seam allowance you are ready to cut your pieces out.
After cutting, you will iron back 1 cm of your seam allowance as follows: on one piece, lets say seat seam, on to the right side of the fabric, on the other piece to the left side of the fabric.

flat-felled seam

Step 3: Folding your seam allowances into each other and pinning the pieces

flat-felled seam folding

Step 4: Sewing
Now sew your pieces together from the right side making the first seam about 0,1 cm from the folded edge and the second one around 0,7 cm from the first seam.

flat-felled seam tutorial

Flat felled seam from the right side

and from the left side

Option Two:

Step 1 - add seam allowances as mentioned before

Step 2 - mark 1 cm on one piece from the cutting edge

Step 3 - place second piece on top of the first one, so that the cutting edge of the second piece is aligned with marks on the first one. 

flat-felled seam tutorial

Pin those two together and sew as shown below.

flat-felled seam tutorial

Step 4 - Fold the seam as shown below, baste if needed and iron it gently.

flat-felled seam tutorial

Step 5 - sew from the right side, making the first seam 0,1 cm from the folded edge and the second one about 0,7 cm from the first one.

flat-felled seam tutorial


  1. I am guessing this cannot be done in the way you describe on a home consumer-grade machine? Because, for example, on jeans, I'd end up sewing one side of the pantleg to the other. There has to be some type of "tube" to slide the pantleg over?

    1. Hey Matt,

      It absolutely can be done on a home sewing machine. I sew my back crotch before I sew the inseam on pant legs. I usually topstitch or flat-fell my inseams.
      I make my jean back legs so - yoke, pockets, back crotch.

    2. Come to think of it you can even do it after you've sewn your pant legs together :)

    3. Alright, I'll try it when I get to that part...(I'm still working on the pocket lining attachment step of my jeans pattern)

      Your explanation of doing it seems the simplest method out of some others I read elsewhere. It will probably be easier for me to visualize when I actually do it.

  2. Thank you for explaining the right way to do a flat felled seam. I was trying to copy my son's karate pants and was stumped on the seams. I finished the pants thanks to you.

  3. Would this also work on a curved seam like the back crotch? I'm having a hard timing picture how to get the left and right sides to match up, since the curves are going in opposite directions. Thanks.

    1. Yes it will work with a curved seam.
      Try option two if in doubt. Mark at least 3 notches with pencil on the most curvy part on bouth of your pieces, align and pin your pieces making sure that the marks line up aswell and then make the first seam.

  4. Great post! So for method 1, you basically fold and press 2/3 of the seam allowance so that when the seams are stitched, the original seam line will fall between the rows of top-stitching. Brilliant!