What Is Understitch In Sewing?

Understitch is a row of machine stitches that are sewn parallel to a seam line, usually 1/8″ away from the edge. The purpose of understitching is to keep the seam allowances from rolling to the top side of the garment and to help stabilize a seam. Understitching can be sewn with either a straight stitch or zigzag stitch.

WHAT IS UNDERSTITCHING? Why you don't want to skip this crucial sewing step (esp. for pro finishes)!

An understitch is a type of stitch used in sewing that helps to secure the seam allowance to the garment. It is usually sewn just inside the seam line and helps to prevent the fabric from rolling or bunching up. Understitches are often used on curved seams, such as necklines or armholes, to help keep them looking smooth and finished.

Understitching by Hand

Understitching is a technique used in sewing to make sure that a seam stays flat and doesn’t pucker. It’s done by stitching just below the seamline on the wrong side of the fabric, usually with a contrasting thread color. This creates a little “ledge” of sorts for the seam to sit on, which keeps it from curling up and looking messy.

Understitching is most often seen on collars, lapels, and plackets (the area where a buttonhole is), but it can be used anywhere you want to make sure a seam lies flat. It’s a good idea to understitch any time you’re working with lightweight or delicate fabrics, as well as when you’re joining two pieces of fabric together at an angle (like on a bias-cut skirt). To understitch by hand, start by pressing your seam open.

Then, using a hand-sewing needle and thread, stitch along the seamline about 1/8″ away from it. Be careful not to catch any of the other fabric layers in your stitches! When you get to the end of the seam, knot your thread securely and trim any excess.

What Is Understitch In Sewing?

Credit: historicalsewing.com

Do You Need to Understitch?

When it comes to sewing, there are a lot of terms that get thrown around that can be confusing for beginners. One of those terms is “understitching”. So, what is understitching and do you need to do it?

Understitching is a sewing technique where you sew a line of stitches close to the edge of a seam allowance. This helps to keep the seam allowance from rolling to the top side of your garment or project. It also helps to stabilize the seam and prevent it from stretching out over time.

So, do you need to understitch? That depends on your project and personal preference. If you’re working on something that will see a lot of wear and tear, like a garment or bag, then understitching can be helpful in extending the life of your project.

If you’re working on something that doesn’t need to be as durable, like a pillow cover or quilt block, then understitching may not be necessary. Ultimately, it’s up to you whether or not you want to take the extra step of understitching your seams.

How Do You Understitch on a Machine?

If you’re looking to achieve a polished look on your garments, understitching is a great way to do it. Understitching is when you stitch along the edge of a seam allowance, usually close to the seam line. This creates a stabilizing effect and helps keep the seam allowance from rolling to the garment’s right side.

It’s also helpful in preventing gaping at necklines and armholes. There are a few different ways that you can understitch on a machine. The first is by using a straight stitch.

Set your machine to a longer stitch length- around 3mm- and sew along the edge of the seam allowance, making sure to catch both layers of fabric. You can also use an overcast stitch or serger for understitching, which will give you added security and strength. Understitching is most commonly seen on facings and linings, but it can be used anywhere you want extra stability or want to prevent gaping.

Give it a try next time you’re sewing!

What is the Difference between Top Stitch And Understitch?

Top stitch is a type of stitching that goes through the top layer of fabric and often creates a decorative stitch. Understitch is a type of stitching that goes through the bottom layer of fabric and helps to keep facings in place.

How Do You Understitch a Hem?

Understitching is a sewing technique used to finish raw edges and prevent them from rolling to the outside of a garment. It’s often used on necklines, armholes, and hemlines. To understitch, sew a line of stitching parallel to the raw edge, just inside the seam allowance.

This will anchor the seam allowance in place and help it lie flat.


Understitching is a sewing technique that involves stitching along the seam line of a garment, usually on the underside of the collar or lapel. This helps to keep the garment’s shape and prevents it from stretching out of shape. Understitching can also be used to create a decorative effect on a garment.


I’m Jane and I’m the editor of janesknittingkits.com! I am a long-time craft and clothing design fan who has been writing about these interests for years.

I have spent many hours studying knitting, weaving, sewing, embroidery, and quilting as well as learning about various brands and models of sewing gear and machines. In addition to this research, my work involves publishing information related to these topics in ways that will be informative for both amateur crafters like me and more experienced sewers!