How to Resize a Hat Knitting Pattern

Getting Your Head Around the Math

USA, Utah, Lehi, Young woman knitting woolly hat
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A common question that knitters have when they feel confident enough to branch out from written knitting patterns has to do with resizing a project. They may want to, for example, size an adult hat knitting pattern down to a child's size, or make a hat that's written for a baby for an older child.

The good news is that most hat knitting patterns are relatively easy to resize; the only trick comes with intricate pattern stitches, cables or colorwork that you might have to adjust to make the hat look right.

Sizing Down

First, let's take a look at a really easy hat pattern and try to make it smaller. We'll be using the figures from the Scarf Hat, a simple Stockinette Stitch hat with a Garter Stitch edge, for the math.

This hat is intended to fit a teen or small woman, but what if you wanted to make one for, say, a 5-year-old?

Sizing for hats can be a bit tricky because everyone's head is a different size and grows at a different rate. You can use the charts at Bev's Country Cottage as a general guideline if you don't have the person I'm knitting for nearby to measure.

This chart tells us that a 5-year-old should have a head that's between 19 and 20.5 inches. Since that age group is 4 to 10, somewhere closer to 19 would probably work. Since hats are stretchy, you can knit a hat that's smaller than the actual head circumference and it will still fit just fine.

The chart also suggests the hat should be 8.5 inches deep.

On this particular hat, you could go a shorter than that because the scarf serves as earflaps (the teen sized hat is only 7.5 inches, for example).

Now that you have your measurements you should knit a gauge swatch to see how many stitches per inch you're getting with your chosen yarn. Because you're basically rewriting the pattern, you can choose a yarn that gives you a different gauge and just adjust your math accordingly.

For the sake of ease, though, let's assume we have 5 stitches to the inch, just like the pattern suggests. If we want to knit a hat that's 19 inches around, we'll want to cast on 95 stitches (5 times 19).

Does that number work for the rest of the pattern? Given that this hat is made of Garter and Stockinette stitches, yes, it does. It also works with how the decreases are written. Decreases on the original pattern start with a knit 3, knit 2 together round, which requires multiples of 5 to come out evenly. 95 divides evenly by 5, so this pattern will work with no changes other than to the number of stitches cast on and the length of the hat.

Sizing Up

Working in the other direction is pretty much the same. This time let's look at the Seed Stitch Baby Hat and assume we want to knit it for a toddler, let's say a 1-year-old.

Going back to the sizing chart again, we see the circumference of a toddler's head can range from 18 to 20 inches; let's say we want the finished hat to be 17 inches to allow it to stretch to fit. It also suggests 8 inches for the length.

Again you'd want to knit a gauge swatch, but again we'll assume the same gauge, which is again 5 stitches per inch. If you're trying to knit a 17-inch hat, that will give you 85 stitches (17 times 5).

For both the ribbing and the Seed Stitch used in this pattern, we need a number of stitches that divides by 2, which 85 does not. You can either go up or down a stitch, though, and you'll be fine. Let's try 84 stitches.

Looking at the shaping, round 1 of the decreases shows a wide variety of decreasing options. You might want to get out your calculator and see what 84 divides evenly into. The answer is 4, so the easiest thing to do would be to skip that first round of decreases and start with a round of work 2, work 2 together (which takes up 4 stitches each time). It won't make a huge difference in the finished hat.

The Basic Concept

These two examples use really simple patterns where the math happened to work out pretty easily, but the same concepts hold no matter what kind of pattern the design uses.

  1. Figure out the size you want.
  2. Knit a gauge swatch.
  3. Multiply stitches per inch by inches required to get approximate cast on number.
  4. Refine as needed to fit with the stitch pattern and the decrease pattern, or change the rate of decrease as needed.
  5. Decide how long you want your hat to be.
  6. Knit and enjoy your new hat!