Project 001: How to draft gathers
Today we'll be talking about ratios while we learn how to draft gathers.
Hello friends! Today we're digging into how to draft gathers. This post is the second exercise in our Elastic Waist Tiered Skirt project. If you missed our first exercise—How to Draft an Elastic Waistband, you can read it here.
In this post, I’ll discuss what gathers are, compare different ratios of fabric, how to draft your own gathered pattern piece, and some design considerations. Plus, just for fun a little extra math. Let’s get started!
The Basics
Fundamentally, gathers are when one piece of fabric is scrunched up and sewn to a smaller, flat piece of fabric. A gathered effect can also be created with elastic or a drawstring (similar to when you cinch closed the top of a garbage bag).
In our tiered skirt (see graphic above), we have two sets of gathers sewn between the tiers of the skirt. Plus, a gathered effect is created at the waist by the elastic. In this design, each tier of the skirt is wider than the one above, creating a graduated fullness that increases towardsthe hem.
Gathers are great for creating volume and design ease, often with really simple shapes, like rectangles. They're a very common feature in garments and pretty forgiving to work with. (In comparison, pleats are the same idea but require more precision when sewing and drafting.)
If you are wondering how to sew gathers, I have a video and blog post on my sewing pattern website Sew DIY. Check it out here.
Drafting Gathers
Mathematically, gathers are all about ratios; namely the ratio of the flat fabric to the gathered fabric. (In case you don't remember this from math class, a ratio is a comparison between two numbers.)
I think the easiest way to decide how much fullness is to look at actual samples. I created a series of gathered samples using different ratios of fabric. In these examples, the fabric at the top is a set width (X) and the bottom gathered fabric width is larger ranging from 1.25 times to 2.5 times larger.
You can see in the image above that as the difference between the two numbers increases, we also have an increase in the amount of gathers. Or, the greater the multiplier, the greater the gathers.
By looking at the examples, you can select the look that you want to achieve with your garment. Sometimes, you might want just a little bit of gathers, like at the wrist of a blouse so you’ll use a 1 : 1.25 ratio. Or, if you want a very full gathered skirt, you could use a 1 : 2.5 ratio. With time, you’ll likely find a favorite ratio. Personally, I really like 1 : 1.75.
Other considerations
That said, when deciding on our gathering multiplier, we also want to consider the fabric weight and design of the garment.
Fabric weight A higher ratio of gathers can become heavy and difficult to sew. The heavier the fabric, the more challenging it will be to gather the fabric and stitch through the layers. In these examples, I’m using a medium-weight, loosely woven fabric. If I was using a denim or canvas, it would have been harder to sew through a 1 : 2.5 ratio of gathers.
Garment weight Additionally, the more gathers you use, the heavier the finished garment will be. If you are sewing a maxi skirt or dress with a lot of tiers or thin straps, you might want to opt for a lower gathering ratio and reduce the overall weight of the garment.
How to Draft a Gathered Pattern Piece
Now, that we’ve explored what gathers are and selected the ideal gathering multiplier for our garment and fabric, it’s time to design our pattern piece. For the Tiered Skirt we’re making, we will have three tiers of gathers. You can also use this method to add a peplum to a top, a gathered skirt to a bodice or ruffles to just about anything.
Check out this pattern hack on my blog for adding a gathered skirt to a bodice. This is one of my favorite dresses to wear and it was really easy to make.
For this example, we will start with our Flat Pattern Piece, which I’m calling X. This could be the waistband of a skirt or the bottom of a bodice. Using the finished width measurement of X, we will draft the width of our Gathered Pattern Piece, which I’m calling Y.
A. For this formula, we start with the width of X. (If you are working with an existing pattern, measure the seam line where you want to add the gathered piece, subtracting the seam allowance.) This is A.
B. Next, select the multiplier. This is the second number in the ratios we looked at above. For example, if you want a lot of gathers, use 2.5. If you want fewer gathers select 1.5.
C. Finally, we need to add seam allowance.
To determine the width of the gathered pattern piece, first multiply the width of X by the Multiplier B. Then add two times the seam allowance.
Mathematically, this looks like (A x B) + (C x 2) = Width of Gathered Piece Y.
More simply, the formula is AB + 2C = Y
Example Gathered Pattern Piece
Let’s look at an example. I will imagine that I’m adding a peplum to the bottom of a top. Let’s say the bottom of the front bodice pattern piece is 24”. I really like a medium amount of gathers, so I will use a multiplier of 1.75. And, I’ll use my preferred seam allowance of .5”.
A = 24”
B = 1.75”
C = .5”
(A x B) + (C x 2) = Width of Gathered Piece Y
(24 x 1.75) + (.5 x 2)=
42 + 1 = 43
So, for my example, I need to cut the front peplum 43” wide. (To determine the length, I would add up desired length plus seam allowance and hem allowance.)
How exact do you need to be?
The good news is that drafting gathers is very forgiving and you do not need to be very exact. Adding or removing an inch here and there will usually not make a significant difference. (The smaller the project, the bigger the impact of adding an inch or two.)
When sewing gathered skirts, I will often let the width of my fabric dictate how gathered the fabric will be. I prefer to make fewer cuts in the fabric and maximize my usage, rather than making sure every gather is an exact ratio.
So, if you want to take a more casual approach to drafting gathers, that’s totally ok. I think it’s good to understand the theory behind it though before you break the rules.
How to add gathers to an existing pattern
If you have dabbled in pattern drafting, adjustments or hacking, you have probably hear the term “slash and spread”. Slash and spread simply means you cut the pattern and then spread the two pieces apart. And it’s a way that you can add gathers to a pattern piece.
In the graphic above, I show two different ways to add gathers to a set-in sleeve. To add gathers to the sleeve cap and the wrist, cut the pattern all the way down the middle and spread apart your desired amount. When stitching, gather along the added fabric.
To add gathers to only the sleeve cap, cut the pattern from the sleeve head but stop at the seam allowance at the bottom. You’ll then rotate the two halves away from each other, adding a pie shaped wedge to the middle. Redraw the hem at the wrist to match the original seam line.
How to Simplify Ratios
One final math lesson before I sign off today. If you want to get a little nerdy with the math or you don't want to work with decimals, you can simplify (aka convert) the ratios to only use integers (aka whole numbers). In all honesty, you don't need to get too deep into these ratios when drafting the gathers. I just think it's fun to play around with.
To do this, you want to look at the decimal and think of a multiplier that will make that decimal a whole number. I think the easiest approach is to convert the decimal numbers to fractions, then multiply both sides of the ratio by the denominator in the fraction. For example, 1:1.25 becomes 4:5 with a multiplier of 4.
I hope you enjoyed this post and found it helpful. Next week we will draft the full skirt! You can support this newsletter by sharing with friends and clicking the “heart” symbol at the top or bottom of this page.
Happy sewing!
Beth