Project 001: How to Draft an Elastic Waist Tiered Skirt

Today's the big day where we draft all the pattern pieces to make an elastic waist tiered skirt to your own custom measurements.

This tutorial is utilizing what we covered in the previous two lessons. Check them out here:

Project 001: How to draft an elastic waistband

Project 001: How to draft gathers

About this skirt

This skirt features three tiers and an elastic waistband. This drafting lesson will show you how to draft a skirt of any finished length with these exact design proportions. (Of course, this is just one way to design a tiered skirt. You can use any number of tiers in any design proportions you like. In next week's newsletter, I'll talk more about this.)

Pattern pieces

This skirt requires four pattern pieces and, lucky for us, they are all rectangles. The pattern pieces are the same for the front and back and you’ll need to cut two of each. The Waistband is the same width as Tier 1 and the waist will be fitted with elastic. This approach makes drafting really easy and ensures that it will be easy to take the skirt on and off.

1. Waistband Front/Back

2. Tier 1 Front/Back

3. Tier 2 Front/Back

4. Tier 3 Front/Back

Our approach to today's lesson

I've broken down the process into four sections.

Part 1: Collect information (Write down all the measurements, ease, seam allowance, etc.)

Part 2: Draft Widths (These calculations rely on what we learned in the previous two lessons)

Part 3: Draft the Lengths (We're going to use algebra to create a formula for tiers of graduated lengths.)

Part 4: Recap everything into a handy worksheet

Part 1 Collect Information

Let’s start by gathering all the numbers we need to draft the skirt. There will be a couple of body measurements but the rest are your choice. You get to be the designer and make it your own. Isn’t it great to be in control?

I’ve assigned a representative letter to each number we’ll need. I’ll use these letters to write the drafting formulas. When drafting your skirt, you’ll replace the letters with your own numbers.

A Hip (or waist) measurement For this skirt, you need to measure your waist circumference and hip circumference. For drafting, use the larger measurement of the two.

B Final garment length Decide how long you want your finished skirt to be. My intention with the three tiers is for a maxi/ankle length skirt.

C Desired ease at hips (or waist) (Personally, I like at least 4" of ease in an elastic waist skirt. It's my sweet spot of not too tight and not too loose. You may want more or less. For this style, I recommend at least 5" of ease.)

D Gathers multiplier (See the previous lesson on gathers to choose your multiplier.)

E Elastic width (Using “width” here is a bit of a misnomer but that’s how it’s labeled in the store. Don’t think too hard about it.)

F Elastic Casing Ease (See the earlier lesson on drafting the waistband for more info on this.)

G Seam allowance

H Hem allowance

Part 2: Draft the Widths

The key measurement for drafting the widths of the pattern pieces is the hip/waist measurement A. We will use the finished width of the hip area and the gathering multiplier to calculate all of the tiers.

The expression (A + C)/2 is used repeatedly when calculating the widths. This expression represents half of the body circumference plus ease. If you were to measure the finished garment at the hip from left to right, it would equal this. (We divide by two because there will be a pattern piece for the front and for the back.)

TIP: When drafting, it may be easier to solve for (A+C)/2 at the beginning and make note of this number.

The Waistband and Tier 1 have the same width. It is (A + C)/2 + G×2, our finished width plus seam allowance for each side of the pattern piece.

To calculate Tier 2, we multiply our starting expression by D—The Gathers Multiplier. That formula is, D×((A + C)/2) + G×2.

To calculate Tier 3, we multiply by D again and then add the seam allowance. That formula is, D×D×((A + C)/2)  + G×2.

Using the same gathering multiplier D to calculate Tier 2 and Tier 3 should ensure that there is an equal amount of gathers in each tier. Remember that the amount you gather is personal choice and a higher number requires more fabric. I will often lower the multiplier a little bit to save fabric.

Part 3: Draft the Lengths

The easiest way to draft the skirt would be to say, "make three tiers, each to your desired length". Or, I could provide a set of dimensions for you to follow. But, I wanted to explore how to calculate the length of a tier according to a certain set of design proportions. This way, you can create the same skirt design regardless of your height. For instance, I'm almost 6' tall, so a maxi skirt for my height is not going to be the same length as someone who is 5'2".

This approach is not the easiest way to draft the lengths but it's more precise. And, hopefully, you'll find it fun too!

(A side note on vocab. In mathematics, the word proportion is used to compare two ratios. In design, it's used to evaluate visual balance. For clarity, I will say "design proportion" when using it as a visual reference. I do aim for precision. :)

For this design, I decided to make the top tier the shortest, the middle a little longer and the bottom even longer. To draft our tiers to these graduated lengths, we're going to use algebra. (TBH, algebra was always one of my favorite math classes.) After lots of playing around with different design proportions, I settled on making our middle tier "x" height, the top tier ".75x" and the bottom tier "1.5x". The third tier is twice as long as the top and the middle, is, well, right in between.

The lengths of each tier will be based off of "x". To find "x" we will use the finished garment length "B" and waistband length (which is the sum of the Elastic Width E and the Waistband Casing Ease F). I find it really helpful to look at the diagram of our skirt. B is the total finished length (right side of graphic) and it equals the sum of the waistband and tiers (left side of graphic).

This gives us the following equation.

B = E + F + .75x + x + 1.5x

(Now, we simplify to solve for "x". First, subtract E and F from both sides.)

B−E−F = .75x + x + 1.5x

(Then, add up the "x" values on the right side of the equation.)

B−E−F = 3.25x

(Finally, divide both sides by 3.25.)

(B−E−F)/3.25 = x

This expression represents the finished length of the middle tier. You’ll see it repeated in the length calculations. Just like our formulas for the waistband widths, we now have an expression that will help us draft the tiers. I recommend solving for "x" and keeping this number handy.

In exercise one, we learned how to draft the length of the waistband using the width of the elastic. Our Waistband Length is two times the sum of the Elastic Width E plus Casing Ease F and the Seam Allowance G. Everything is multiplied by two because the waistband is folded in half lengthwise.

Waistband Length (E + F + G) × 2. This can also be written (E + F)×2 + G×2

The length of Tier 1 is .75 or 75% of the "x" height plus the seam allowance on each side. So that length is represented by

Tier 1 Length: .75×((B−E−F)/3.25) + G×2

Tier 2 is the "x" height plus the seam allowance on each side. It is represented by

Tier 2 Length: (B−E−F)/3.25 + G×2

Finally Tier 3 is 1.5 times or 150% of the "x" height plus the seam allowance at the top and hem allowance at the bottom.

Tier 3 Length: 1.5×((B−E−F)/3.25) + G + H

When the pattern pieces are drawn, they will look something like the above. The waistband is shown proportionally larger here so that you can see the details.

Part 4: Worksheets & Calculator

I've created some aids to help you draft this tiered skirt. First is a pdf worksheet that you can print out. On page 1, write down on all the notes from Part 1. On page 2, are the formulas for each pattern piece. Click below to download the worksheet.

Sewingwithnumbers Tieredskirt Worksheet

190KB ∙ PDF file

Download

Download

If you want to double check your work, I've also created a Google Sheet that has all of the formulas built in. Type in your notes and measurements from Part 1 and the dimensions will be automatically calculated for you. Kind of magic! That said, I have tested the Google Sheet on my own but have not had it tested by anyone else. So, let me know if it's working or not working for you.

Click here to access the Google Sheet Calculator. To use the calculator, go to File > Make a copy or File > Download.

I hope that you enjoyed this tutorial! Next week, I will share more about design proportions and how to calculate lengths for other tiered designs. If you enjoyed this newsletter, you can support by sharing or clicking the heart at the top or bottom of the post.

These resources are FREE to use for the time being. I am planning to turn on paid subscriptions for Substack in the future and will likely archive this post. At that time, it will only be available to subscribers. So, make sure to download and save now, if you're interested.

Happy mathing!

Beth