How to Make Sure Your Hat Will Fit

When you decide to knit a hat, ideally you want it to fit when you’re finished. Knitting a gauge swatch and then adjusting either your yarn, needles, or something about the pattern will help ensure it fits as intended when you’re finished. The other option is to dive in, knit as directed, and if it doesn’t fit at the end you’ll need to either give it away or frog the whole thing and make it again. I’m more of a planner and am willing to invest time at the beginning to make sure it will fit in the end.  

Determine Your Gauge

If your pattern gives you a gauge measurement, then simply knit a swatch, adjust your needle size until you can obtain the correct gauge, and off you go. If your pattern doesn’t provide a gauge, or if you want to adjust something about the pattern (such as the size of yarn or to make it for a different sized head than intended), or if you want to make up your own pattern, the information here can get you started.  

It all begins with a gauge swatch, so start by reading this post and knitting your swatch. If you want to design a hat from scratch, start with the needle size recommended for the yarn you want to use. Remember to knit in the pattern for the main part of your hat, and remember to knit your swatch in the round (see gauge swatch post for how to do that.)  

Measure Your Head

After you know how many stitches you get per inch, the next step is to figure out how many stitches will fit your head (or the head of the person for whom you’re knitting the hat.) Measure your head with a flexible measuring tape. You want to measure the widest part of your head, over your forehead, over your hair, just above your ears, and around the widest part at the back. Keep the measuring tape comfortably snug. 

Adjust for Negative Ease

Next you need to adjust for negative ease.  You want the finished hat to be a little smaller than your head so it’s snug enough to stay on comfortably.  Subtract 2” for negative ease if you want the hat to fit snugly, or 1” if you want it to fit loosely. You might want a little more negative ease for a very stretchy pattern (such as ribbing), perhaps subtracting one more inch from the total circumference; if the pattern has very little give (such as cables) you might want to reduce the amount of negative ease by an inch. 

Determine Your Target Number of Stitches

Here’s the math to determine your target number of stitches:

  • The gauge for my swatch knit in my hat pattern is 18.5 stitches across 4”; after dividing 18.5 by 4 I get 4.625 stitches per inch.  
  • The circumference of my head is 22”.
  • I’m knitting a hat that’s a little slouchy but the pattern is very stretchy so I’m going to subtract 3” for negative ease, which brings my target to 19”.
  • 4.625 stitches per inch (my gauge) times 19 inches (my target) equals 87.875 stitches, which I’m going to round to 88.  That means I would ideally cast on 88 stitches to end up with a hat in that specific yarn with those specific needles that will fit my head.  

Adjust the Pattern

The next step is to adjust the pattern, if necessary.  Let’s say my pattern says to cast on 84 stitches, and there’s a 12 stitch repeat in the pattern.  That means I could either cast on 84 or or 96.  I don’t want my hat to be too loose so I would likely round my 88 stitches down to 84.  

Final Tips

When you do ribbing, you’ll want to go down between 1 and 3 needles sizes, otherwise the ribbing will look like it’s a bigger stitch than your pattern (and your hat will likely be too loose.)  

As for the length, I typically follow the pattern and then try on the hat as I go, particularly before beginning the decreases.  If the circular needle you’re using to knit is too small for you to try on the hat, you can add a cable extender and a second cable just to try it on, then remove the extra cable to continue knitting. Check out this post for a video on how to do that.

With that information, you can knit any hat pattern to fit or design your own!  Happy knitting!

Want to Give it a Try?

Here are some hat patterns you might like:

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