How To Put Gussets In a Dress or Top

Update: October 19, 2020

Do you know what a gusset is?

It’s an inverted triangular (or diamond shaped) piece of fabric inserted into a garment to make it fit more comfortably.

If you’d like to put gussets in pants or a top that has sleeves, look at this post on How To Put Gussets in Pants or Shirts.

This post will cover how to put gussets in an area where two seams intersect. These triangular gussets are usually found in a strapless dress or a dress or top that has straps, but no sleeves.

When adding gussets to a strapless dress or top, you will usually have two gussets….one in each side seam, even if you have a zipper on the side.

You know you need a gusset, when you are zipping up a dress or skirt and it won’t zip up all the way.

(There are other instances where they are needed, but we’ll focus on this problem for now.)

If your dress is really tight and you can’t zip it up over the bust, I’ve written a post that teaches you how to put a corset back in your dress , but not every dress needs a corset back.

If you need to enlarge a bridesmaids dress, for example, by a few inches and you want all the dresses to look the same from the back, you’ll want to put in gussets instead of a corset back.

I have had a few e-mails asking how to enlarge a garment that’s too small.

And I get several customers each year that need this alteration as well.

In August,  my daughter came back home for the weekend to be a bridesmaid in a friend’s wedding and the bodice of her dress was too tight to zip up.

She ordered it in the same size as the one she tried on in the bridal store, but the one that came in didn’t fit the same as the one she tried on. And of course, there wasn’t time to get another dress.

Unfortunately, this is a common problem.

So, with about two hours to spare, I knew what it needed.

You guessed it: gussets.

This long thin pie-shaped insert is a gusset:

Side view of Michelle's black bridesmaid dress with gusset in the dress

Just so you know, the gathered fabric to the right of the gusset is a tie that was sewn into the dress and it tied around the waist.

Here’s what it looks like with the ties pulled away from the bodice:

Photo of the top half of Michelle's black bridesmaid dress with the chiffon ties floating above, Sewing Garden

Chances are, your garment won’t have ties like this, but if it does, you don’t have to take them out.

Just ignore them and forget they are there.

Unfortunately, I forgot to take pictures of the gusset-making process when I added these to her dress, because I was in a hurry to get them done before the wedding.

So,  today I’ll show you how to make these gussets using mostly diagrams.

Read all of the instructions before you begin so you are familiar with the process.

Here is a diagram of the back of a dress and what this dilemma looks like. The 2 black vertical lines toward the top of the diagram are the spaghetti straps:

Diagram of what it looks like to measure where a dress or top needs a gusset added, Sewing Garden

To do this alteration, you’ll need to take two measurements.

The dash lines below show what measurements you’ll need to take:

Diagram of the measurements to make a gusset of a top or dress, sewing garden

Let’s say that the opening across the top is 4″ and the measurement down the side of the zipper to the zipper pull is 5″.

Jot your measurements down.

Grab a piece of computer paper (or something of similar size.)

Make a big dot at the top middle of the paper (shown in the diagram below).

This mark will symbolize the center back of the dress. (Notice, we are using the gap in the middle back of the dress to figure out what size gussets will be sewn in the sides of the dress.)

Take the top measurement (in this case, it was 4″) and divide that number in half.

You’ll be making two gussets: one for each side seam of the dress, so that is why you divide the number in half.

In this case that means 2″.

You are basically going to add 2 total inches to the left side of your dress and 2 total inches to the right side. (Adding them up equals the 4″ total that you need to make the dress fit.)

Now we are going to make one of the gussets first.

Measure out to the left of that main dot one inch and make a second dot. Now, measure out one inch to the right of that first dot and draw another dot, just like in the photo below.

Then, measure down 5″ from the first dot (or whatever your second measurement is) and make another dot.

Connect the dots with a ruler like this:

Diagram of making the first few dots to draw the gusset shape for a dress or top, sewing garden

As you can see, the measurement that is horizontal, represents half the opening you have in your dress along the top (because this is only one of the two gussets.)

The vertical line represents the opening you have from the top of the dress down to the zipper.

Make sense so far?

Ok, now draw a line from the outer dots to the bottom dot like this:

Triangle diagram of a gusset after I measured for the dimensions for a gusset for a dress or top. sewing garden

This represents your gusset without seam allowances.

Now, we’ll add the seam allowances.

I add a half inch to the sides and bottom of this triangle, like this:

Adding a seam allowance on a diagram for a gusset for a dress or top, sewing garden

****Whether you have lining in your garment, or not, you’ll need to place the top edge of this triangle on the fold of the fabric scrap you have chosen to make your gusset out of.

Otherwise, if you didn’t place it on the fold, you’d have a raw edge at the top. (Sometimes, when the garment has a seam in the armhole, then I’ll add a seam allowance to the top edge and cut two pieces out and seam them at the top edge before inserting the gusset into the garment.)

But I try to avoid that step if at all possible. Most people can’t see the top of this gusset anyway.

If I don’t have to add the seam allowance at the top edge, I’ll cut this triangle out like this:

photo of a cut out diagram of a gusset with seam allowances for a dress or top gusset, sewing agarden

Again, to me it’s much easier to have a fold at the top edge of the gusset I make.

This means you need to pay attention to how much fabric you need to make the gusset out of.

I try to match the gusset fabric to the main fabric of the garment as best I can, from the scraps I have around the house.

Many times my customers think that if I take a few inches off the hem of the dress, I’ll have enough to work with, but many times I don’t. Most of the time, that hem scrap is curved and I don’t get a full triangle piece when I place that pattern on the fold of the scrap.

You may have to go and buy a small piece of fabric (a quarter yard is usually plenty) that matches.

Once you do that, place the top edge of the pattern you just cut out of paper on the folded edge of the fabric and cut it out along the lines.

Press the top edge of the gusset piece with an iron to set that fold.

Many times, I’ll iron on interfacing on the inside of the back piece of that triangle. (If you do use interfacing, you can make it the size of the interior of the pie piece without seam allowances if it is iron on interfacing. If it is sew in interfacing, use the entire gusset pattern to make the pie piece and then stitch it onto the gusset piece before proceeding.)

The interfacing will add some stiffness and body to the gusset piece. I don’t iron on interfacing to the front of the triangle piece because many times it gives it a very stiff look or a bubbly look, instead of the soft satin look. Adding interfacing to the back should be enough added support for the gusset.

Now, mark the seam allowances on the gusset pieces.

Mark those dots on the gusset piece too (except you don’t need to mark that center back dot.)

Now, set aside the gusset pieces and pick up your garment.

Looking at the garment where the side seam meets the underarm, you may have understitching there.

See the horizontal stitches in the photo below?

Photo of a seam ripper taking out the stitches in Michelle's black bridesmaid top preparing for a gusset.

I’ll take out twice as many as I think I need to work in that area.

Take apart the side seam.

You may have boning in there.

Remove it and mark which way the boning came out. You don’t want to get it in backwards or upside down when you put it back in.

Then, take out the side seam stitches, only and exactly to the 5 inch mark (or whatever your measurement was…no more!)

Lay the gusset (right sides together) to the right side of the dress, matching the seam allowance line of the gusset to the stitching line of the dress.

Match the top dots to the top edge of the dress.

Match the bottom dot to the 5 inch mark, right at the point where you stopped when you took out the side seam.

You’re only matching and sewing the front edge of the gusset right now. (However, if your garment does not have lining, you can match the entire folded gusset to the seam allowances now.)

Using the original seamline as your guide, stitch along one side of the gusset, starting at the fold area and sewing down to the 5″ spot.

Backstitch and cut your threads.

Now, stitch along the other edge of the gusset from the top fold down to the 5″ spot again.

Check to make sure you don’t have any bumps or haven’t caught any stray fabric in that seam.

If you have done that, rip it out and restitch it.

If you don’t restitch it, it won’t lay flat on the outside of the dress.

Next, pin the other end of the gusset to the lining, matching it in the same way you did the original end.

Stitch. Then, double check your stitching again.

If you need to put boning back into the dress, add it to the side of the gusset that is closest to the back of your dress.

You can stitch through the boning (if it’s not the heavy plastic kind.)

If it is the heavy plastic kind, you can make a casing in the side seams by stitching the outer edge of the gusset and that back side seam.

Then, slide that boning right down into that casing.

Then, I push the seam allowance to the back and tack that casing to the lining, if necessary, so it doesn’t move.

The gusset should look and lay flat.

You shouldn’t need to iron it at all.

I like that, because many bridal or formalwear garments are made of un-iron-able (is that a word?!) fabrics.

Now, sew the other gusset into the other side seam of your garment.

If you measured correctly, this dress will be perfect!

So, here is the photo of it again:

Side view of Michelle's black bridesmaid dress where I put the gusset in, Sewing Garden

If the top edge of your gusset looks a little wavy, don’t be alarmed.

When you, or your customer, or family member puts it on, that waviness will disappear.

Most likely it’s wavy because it is a fitted garment and it’s not on the person yet.

Now, have them try it on and you’ll be the new hero because they can zip it up!

It looks great,  and they can now breathe easy and so can you!