The Math Behind the Dress

I’m a math nerd. LOVE it. In High School I was on the math team, meaning I took math tests outside of school. For fun.

Knitting has so much math behind it. To just make something it is mostly counting; but to design or adjust fit of a garment… so much math. Mostly geometry, a little basic algebra.

After I drafted the paper pattern for my dress, I broke out my trusty T-square, calculator, and pattern swatches. Most of the time I won’t get super far into the details of work, but this post is the exception. If you don’t like math, the tl;dr (“too long, didn’t read”) version is:

I wrote out the knitting pattern based on when and where increases/decreases were needed to replicate the pattern pieces.

For my fellow nerds… Here’s the full process:

Step 1: Create plumb lines

For the example, I will show the center. I call it pattern piece A.

  1. Across the bottom of the dress, draw a straight line from one edge of the curve to the other. (Line 1)
  2. Measure the half way point on this line. Draw a line at this half way point at 90 degrees from the first line across the entire pattern piece. (Line 2)
  3. Align the rule with the angle from the bottom edge of the dress on the left side. Mark the point where the pattern no longer follows the ruler. Draw a line connecting this point to Line 1 with a 90 degree angle (T-square to the rescue!) (Line 3)
  4. Repeat step 3 for all major angle changes

For Piece A, the piece is (or should be!) symmetrical so only one side needs to be measured. The other pieces require continuing step 1 on both sides.


Step 2: Measure

Measure all the lines. The angle, horizontal line, and vertical lines give us right triangles. The whole pattern is broken down into triangles with the exception of the curve at the bottom.

Step 3: Determine pattern change points

This is a less formal step. It seems more like a design step, but is also super important for writing the pattern!

Here are my finalized stitch patterns and break points (from bottom to top, finished measurements)

  • Ingrid Rüütli Kiri and Silvia Kiri – 19″
  • Stockinette – 12″
  • Frost flowers and modified frost flowers – to top

Step 4: Calculate

So the cool thing about right triangles is that they are easy to expand or shrink and keep the same angles. If you double the length of one side, to get the equivalent triangle all the other sides are doubled. Easy math.

Why is this important?

Because lace needs to be blocked. If I tried to knit the pattern directly, after I blocked it, the dress would be several sizes too large. To get the ending measurements to line up with my paper pattern, my pattern needs to be adjusted down based on how much the fabric grows when blocked.


Oh and by the way, each stitch pattern has a different conversion/ growth rate. THAT’s why I did swatches. I measured before and after blocking to get my conversion, plus kept track of my stitch and row count.

The cool thing is by doing the math I will have both knit measurements and expected stitch counts to double check my garment along the way.

Step 5: Write the Pattern

Most of the work for this step is really done in the previous one, but this is where I go from measurements and notes to translating to “Knit-ease” (the knitting language). I’m placing the increases on the sides, rather than evenly spaced throughout the row. I decided on using “Make One”s for the seam increases (M1L and M1R). I added notations to place markers (PM) to indicate the center, where the pattern repeats start. Decided where to place beads…

A little tangent (True AND a math joke!): I love, love, LOVE this little notebook/ planner I started using for this. It has grids and blank pages. SOO useful for writing out patterns and charting them! I can easily switch back and forth.

Le fin: I suppose technically if I typed this up it could be a pattern to sell. In only one size. Do people buy patterns in only one size?

What about you?

How do you use math in your daily life?


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