How to Measure and/or Determine Your Hat Size

Adjustable hats are great. That snap-button or Velcro closure in the back does wonders for making sure that a branded baseball cap will fit just about anyone who receives it. Some custom hats require you to know your hat size, which we’re going to learn how to measure in this handy article.

Sometimes, though, you want the personalized fit and attractive design that comes with a non-adjustable cap. In that case, it’s important for you to know your hat size. Don’t worry; it’s not nearly as frustrating as shopping for jeans. In fact, with just a tape measure (or a long piece of string and a ruler) and the handy guide below, you can figure out your hat size!

Step 1 Measure Yourself!

You’re going to look pretty goofy doing this. Just a heads up.

Take your tape measure and wrap it around your head (not too tightly) at the widest part, where the bottom edge of your hat will most likely rest. For many people, this would be about a half an inch above the eyebrows, or about one-eighth of an inch above the top of the ears.

Hold your thumb or another finger against the tape measure where it comes around to meet the end. Take a look at the measurement you come up with. Congratulations – you now know the circumference of your own head! Be sure to write down your measurement in inches, and if your tape measure has metric units on it, go ahead and write down your measurement in centimeters, too.

Don’t have a tape measure? Don’t worry.

You don’t have to hold a ruler up to your head and try to estimate your size. This is where that long piece of string comes in. Simply wrap that around your head just as you would a tape measure, and then lie the string flat on a table alongside a ruler (remembering to keep your thumb or finger on the spot where the string wrapped all the way around).

Step 2 Calculate Your Size!

Ah, if only it were as easy as just knowing how big your head was (no, not in an ego sense!). Sad to say, most U.S. hat sizes either correspond to a number somewhere between six and eight (which looks nothing like the number you got when you took your measurements) or are listed simply as small, medium, large, or extra-large.

Luckily for you, many respectable hatters provide conversion tables so that you can translate your measurement into a size that you would actually find on a label. But just in case you can’t find a conversion table, here are some handy calculations that you can use to navigate the world of custom headgear:

Hold your thumb or another finger against the tape measure where it comes around to meet the end. Take a look at the measurement you come up with. Congratulations – you now know the circumference of your own head! Be sure to write down your measurement in inches, and if your tape measure has metric units on it, go ahead and write down your measurement in centimeters, too.

To estimate your numerical U.S. hat size, divide the circumference of your head in inches by 3.14. (Psst: remember learning about circles in your high school geometry classes? 3.14 is the approximate value of Pi, which figures in here because, well, heads are kinda round.)

To calculate the circumference of your head in centimeters (more later on why we keep mentioning this), multiply your circumference in inches by 2.54.

But you’re looking for a custom hat, right? That means that you want an accurate fit – which means that you want an accurate conversion chart. No problem! Here’s your guide to U.S. hat sizes:

Circumference (in inches) U.S. Hat Size General Size
20 7/8 6 5/8 Small
21 1/8 6 3/4
21 1/2 6 7/8
21 7/8 7 Medium
22 1/4 7 1/8
22 5/8 7 1/4 Large
23 7 3/8
23 1/2 7 1/2 Extra-Large
23 7/8 7 5/8

But what if my measurement falls in between the ones you have listed? In that case, we recommend choosing the next larger size. Trust us: a hat that’s slightly bigger is much more comfortable, much easier to pad, and much more likely to be worn than one that’s slightly too small.

Step 3 Allow for Some Variation!

The chart above covers a lot of hat-buying situations, but of course, it can’t cover them all:

Many customizable hats are unisex, and if you buy them from a North American retailer, they’ll use the table above. However, some hats are made specifically for men or for women. What does that mean? Well, when shopping for women’s hats, you might still see the size given as the circumference in inches. (Fun fact: men’s hat sizes actually are traditionally determined using the head’s diameter – the measurement straight across from one side to the opposite. It’s because that’s such a chore to physically measure that we use the system outlined in the chart.)

Did you know?

Hat sizes in the United Kingdom are close to U.S. sizes but not entirely the same – British sizes are one-eighth of an inch smaller than U.S. sizes. In other words, a size 7 1/8 hat in the U.S. would be the same as a size 7 British hat.

The European sizing scale uses a metric measurement, which is the measure of the circumference of the head in centimeters. A-ha! That’s why we kept mentioning centimeters –now you can shop far abroad with confidence!

Hat size might seem complicated at first, but once you know what the numbers mean, figuring out the rest is easy. All you need is a tape measure (or a string and a ruler) to measure your head and our handy calculation guide. Armed with the knowledge of how to properly measure hat size, you’re now ready to shop for a custom hat or cap that will put you heads above your competition!