by Daughter Fish

Abandon hope, all ye who enter here: this is going to involve some math!

Didn’t  scare you? Good. Because I’m about to share how to draft my favorite dress of the season.

If you caught my first post on my reimagining of Claire McCardell’s future dress from 1945, you may remember that I promised a tutorial. Like I mentioned in that first post, this dress is completely based off of 4 triangles, cut on the bias, which gives the dress its wonderful drape. Each of the main triangles are divided into three pieces, both as a design element, and as a way to use the fabric efficiently.  There are no closures in this dress, which makes it really easy to sew. The most complicated part of making the dress comes down to drafting those big, divided triangles.

In this tutorial, I’m going to share how to draft the pattern for the long version of this dress (I also make a short version). Because of the size of the triangles, the easiest way to draft this pattern is in miniature scale on a piece of graph paper. All you need is a little aptitude with a ruler, protractor, and a calculator. (That’s my backdoor way of saying, this project requires geometry!).  I also flagrantly use geometry calculators to make everything easier (cheating?! Moi? Never). I’ll share a few online calculators below, but you could also download a free geometry app to your smart device. I wish I’d done this the first time drafting this! I really like The Visual Geometry Calculator for android. Apple sells some geo apps for the iPhone (Math App – Geometry I gets high reviews). If you want to get real fancy, you could also download a free scientific calculator app.

Of course, you could just copy all of my calculations here, but I think there’s a valuable reason to draft the dress to your measurements. One of my favorite aspects of this dress is that you can draft it to fit your height and the width of the fabric you’re working with. This allows you to make a nearly no-waste garment. So, even though the dress does take up a lot of fabric (nearly 6 to 7 yards for this long version!), the pattern pieces can be fit onto your fabric like a big game of tetris, and barely any fabric is wasted.

Here’s what you’ll need:

If you don’t happen to have your grade-school geometry supplies handy, you can download a protractor and graph paper. I printed out 1/2-inch graph paper, because the squares are easy to see and I could divide them easily into the height of my triangle.

You’ll also eventually need large pieces of paper—such as kraft, butcher, or wrapping paper—to make the full scale version of the pattern.

Step 1

Measure from the nape of your neck, down the front of your body to the length of where you want the dress to hit (including seam allowance for a hem). I decided 60 inches was right for me. Counting each box in my 1/2-inch graph paper as 5 inches, I drew a vertical line representing 60 inches.

Step 2

I wanted as much fullness in the dress as I could get out of the fabric. Because I was working from a 60-inch wide bolt, I drew a horizontal line representing 60 inches (again, counting each square as 5 inches). If you’re working from a thinner bolt, 55 or 45 for instance, draw your horizontal line that length, centering it on the vertical line. (Don’t worry about cutting into the selvedge of your fabric, that’ll get eaten up in the seam allowance.)

Step 3

Draw two lines to complete your triangle. You should be looking at an isosceles triangle (has at least two equal sides).

Now you need to figure out the length of those two outer sides. The easiest way to do this is to break the lager triangle into two right triangles:

From geometry class, you might remember old Mr. Pythagorean theorem:  a² + b² = c² .  From there, you can just go wild with your trusty new scientific calculator app. Or, if you always thought Mr. Pythagorean a crusty old bastard, just use a number of online calculators, like this one, or your handy smartphone app to figure out the length of c. In this case it’s 67.

 Step 4

Now you need to figure out the angles inside your triangle. All three angles should add up to 180°. Again there are real math ways to do this, but you could again turn to an online calculator (I like this one) or use your handy protractor. My angles were 53 for the top, and 63 each for the bottom two angles.

Now that we have the measurements of the basic, large triangle, we have to break it into parts.

Step 5

Part of what made Claire McCardell’s original future dress, and my version, visually striking is that within each triangle there are three sections. Once sewn together, the seams joining these sections match up with the seams in the adjoining pattern pieces, creating a big chevron around the dress. You can also use these smaller sections to color block your dress (as I did above). Lastly, breaking the large triangle pattern piece into three sections allows you to use the fabric efficiently. (if you simply cut the large triangle out of the fabric, you’d waste a lot of it).

I divided my triangle so that there would be a diagonal line from my hip down to my thighs. Measuring my body, I determined that this line needed to be 22 inches from neckline (or the top of the larger triangle) to hip, and 33 inches from neck to the front of my thighs. In the sewn dress, this diagonal line meets with the mirrored diagonal line to form the first V in the chevron.

This left me with three sections in the larger triangle, which I broke down into smaller measurements.

Step 6

To draft all of these smaller triangles in the full scale, you have to determine the angles within each of the smaller pieces. For the top triangle, you should already have the lengths of 2 sides of the triangle (22″ and 33″ here) and one angle (53° here). Using your mad geo skills, or this calculator again, you can figure out the last side of the triangle and the other two angles.

Repeat this for the bottom triangle section.

Now you should have the dimensions of the middle section of the larger triangle. All you need now are the angles of the four corners inside this section. The angle of a straight line is 180°, so you can simply subtract the opposite angle on the line from 180°:

Repeat this for the rest of the angles. You should now have all the angles and lengths you need to draft your pattern pieces in the full scale.

Step 7

Using your protractor, a long ruler, and your pattern paper, draft the full-scale versions of the 3 pattern pieces that make up the larger triangle.

 Now you have your full scale pattern, ready to cut out!

But wait…

The future dress gains all of it’s wonderful drape because the pieces hang on the bias, so you need to cut them so they will hang on the bias, like this:

At this point you might be thinking, “great, Fish, you just had us make a big triangle. Now what?!” Never fear, my friends.


To make the dress, simply cut out 4 of each of the pattern pieces (remember that 2 of each of these pattern pieces should be cut so they mirror the other 2 pattern pieces, otherwise the seams of the sections won’t create the pretty chevron around the dress) After cutting out the fabric, sew the 3 sections of each large triangle together, then sew the 4 large triangles together.

You should have something that looks like this:

I inserted inseam pockets, because a good dress always has pockets! Leave the top of the triangles open for the arm and neck openings.

McCardell’s original dress was designed with ties around the neck. Instead, I like to create a halter with the tops of the two front triangles. I then finish the neckline and the top of the back two triangles with a hand-rolled hem, then connect the tops of the back two triangels to the halter.

As with any bias-cut dress, you should let this dress hang on a hanger for a few days, so the fabric has a chance to stretch out. If you hem too soon, you’re libel to eventually end up with an uneven hem.

Hemming the dress is the only step where there’s a little waste, because you cut off the pointy edges at the bottom (unless you like that look, in some case’s that can look great). Because of the length of this dress (and because I don’t have a full-scale form), I find it easiest to hang the dress so that it’s even on the hanger. I then use a measuring tape and tailor’s chalk to measure from the floor to where I want to hem all around the perimeter of the dress and use that as my cutting line. Hem as desired.

If you would like, need, or want a little more direction on how to construct the dress, I’m working on something a little more involved to break down each step.

If you make this dress, I’d love to hear how it goes, If these instructions don’t make sense, or if you have any modifications to add, please let me know (and I’d love to see pictures!). I think the dress would be awfully nice made out of a light silk or even a drape-y wool and layered with an undershirt for the cooler months to come.