You've found the beanie, the fitted cap, or the wide-brim felt hat you want - and the product page wants a size: S/M/L, a number, or a circumference in centimeters, with no store nearby to try it on. Every "how to measure your head for a hat" article repeats the same tape-around-the-skull trick, hands you one generic chart, and stops there. None of them mention that the letter on the chart barely means anything by itself - a Medium at one brand starts where a Small ends at another, and hats are one of the most commonly gifted items that come back for a resize every holiday season.
This guide covers the measuring method that actually works at home, a complete head circumference to hat size conversion chart, the mistakes that quietly throw off a DIY measurement, why you should never trust a letter size alone across brands - and, once you have a number you trust, how to save and compare hats from multiple stores and preview them on your own head with AI try-on before you buy, using a cross-store wishlist like Spree.
Why Guessing Your Hat Size Goes Wrong
There is no single "hat size" the way there's a single head circumference. The letter or number on a hat's tag depends on the brand, the style of hat, and sometimes the specific fabric's stretch. A measurement taken over thick, unflattened hair, held too loosely, or compared against the wrong brand's chart can be off by a full size before you even place the order. That's exactly why the same "Medium" snapback fits perfectly from one brand and sits loose or pinches from another - and why hats bought as holiday or birthday gifts are quietly one of the most returned or re-gifted items of the season.
01
Measuring over thick hair
Voluminous or heavily textured hair can add a centimeter or more to your reading if you don't flatten it first — enough to push you into the wrong size.
02
Tape too loose or too tight
A tape that's pulled snug enough to compress your skin reads smaller than your real size; one left loose reads larger — neither gives you a number you can trust.
03
Trusting the letter, not the centimeters
S/M/L is only loosely standardized — one brand's Medium covers 56-57cm, another's starts at 55cm. The circumference number is what actually travels between brands.
04
One brand's chart, every brand's hat
A fitted cap, a structured felt hat, and a stretch beanie all fit differently at the identical labeled size — the construction matters as much as the number.
The Tape-and-String Method: How to Measure at Home
You'll need a soft (cloth or vinyl) tape measure, or a strip of paper or non-stretchy string and a ruler if that's all you have. The whole thing takes under five minutes.
1
Flatten your hair
If your hair is voluminous, flatten it slightly with your hand or wear it the way you will under the hat - measuring over a thick, unflattened style will inflate your number.
2
Position the tape correctly
Wrap the tape around the widest part of your head: about half an inch above your eyebrows across the mid-forehead, and just above the tops of your ears, keeping it level all the way around.
3
Keep it snug, not tight
The tape should sit snugly against your skin without pressing in or leaving a mark - snug enough that it wouldn't slide, loose enough that you can slip a finger underneath.
4
Read the measurement in centimeters
If you used string or paper, mark the overlap point and measure that length against a ruler afterward. Record the number in centimeters - that's your head circumference, the number hat sizes are actually based on.
5
Measure twice, and round up if you're between sizes
Measure a second time to confirm the number holds. If you land between two sizes on a brand's chart, size up rather than down - a slightly loose hat is more comfortable than one that pinches.
Hat Size Conversion Chart: Head Circumference to Letter Size
Hat sizing is based on head circumference in centimeters first, with letter sizes layered on top loosely and inconsistently by brand. Match your measured circumference to the closest row below, then double-check against the specific brand's own chart before you order.
| Head (cm) |
Head (in) |
Typical Letter |
US Fitted |
| 54 | 21.25 | XS / S | 6 7/8 |
| 55 | 21.65 | S | 7 |
| 56 | 22.05 | S / M | 7 1/8 |
| 57 | 22.44 | M | 7 1/4 |
| 58 | 22.83 | M / L | 7 3/8 |
| 59 | 23.23 | L | 7 1/2 |
| 60 | 23.62 | L / XL | 7 5/8 |
| 61 | 24.02 | XL | 7 3/4 |
| 62 | 24.41 | XL / XXL | 7 7/8 |
| 63 | 24.80 | XXL | 8 |
Treat this chart the way you would a clothing size conversion chart: a reliable starting point, not a guarantee. Some brands use tighter ranges (a Medium that stops at 57cm), others use wider ones, and structured styles like fitted baseball caps run less forgiving than stretch-fit beanies or snapbacks at the same labeled size.
Buying Hats as Gifts: Why Adjustable Styles Win
Hats are a holiday-season staple gift, and they're also one of the easiest gifts to get wrong on size - you can't exactly ask someone to measure their head before a surprise. If you're buying for someone else or you're genuinely between two sizes yourself, favor styles with a stretch-fit band, a snapback strap, or a buckle closure over a rigid fitted size. They flex across a range of head sizes instead of locking you into one number, and they're far less likely to come back for an exchange in January.
What to Do Once You Know Your Size
A circumference number tells you which box to check at checkout - it doesn't tell you which hat, from which store, actually looks right on you. That's a different problem, and it's the one a cross-store wishlist with AI try-on is built for.
1
Save candidates from any store
Get Spree from the App Store, then paste the product URL or share it in from any of 1,000+ stores - the photo, price, and size chart come along automatically.
2
Compare them in one wishlist
Put the beanies, caps, or wide-brim hats you're deciding between into one cross-store wishlist instead of a dozen open tabs, and swipe to narrow them down by price and size chart.
3
Preview it on yourself
Use AI Virtual Try-On on your own photo to see how a specific style actually looks on you before you commit - a product photo on a stock model tells you far less about your own proportions.
Shoppers who used virtual try-on before buying returned items 36% less often (McKinsey, 2025) — fewer obvious mismatches reaching checkout, on accessories just as much as clothing.
If you're sizing more than just a hat for an order, how to measure yourself for online shopping and the sibling guide for ring size cover the rest of the body the same way this guide covers your head.
Frequently Asked Questions
How can I find my hat size at home without going to a store?
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Wrap a soft tape measure (or a strip of paper or string) around your head about half an inch above your eyebrows and just above your ears, at the widest part of your skull. Keep it level and snug without pressing into your skin, measure twice to confirm, then match the circumference in centimeters to a hat size chart. Flatten voluminous hair first so it doesn't inflate the number.
Is the tape-measure method actually accurate?
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It's accurate enough to get within about a centimeter for most people, which is usually close enough to pick the right letter size, but it isn't a professional hatter's fitting. A tape held too loosely or too tightly, or measured above a thick hairstyle, can shift the reading by a centimeter or more - enough to land you between two sizes.
Does hair or hairstyle affect the measurement?
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Yes. Thick, voluminous, or heavily textured hair can add a centimeter or more to your reading if you measure over it without flattening it first. Measure the way you'd actually wear the hat - if you usually wear it over loose hair, measure over loose (but lightly flattened) hair; if you'd wear it bald or with hair tied back, measure that way instead.
Do hat sizes differ between brands, and is letter sizing reliable?
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Yes, significantly. Letter sizes like S/M/L are only loosely standardized - one brand's Medium might cover 56-57cm while another's starts at 55cm or runs to 58cm, and some brands use combined labels like S/M or M/L instead of single letters. Your head circumference in centimeters is the one number that stays constant; always check the specific brand's own chart before ordering by letter size alone.
Does Spree help with hat sizing?
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Not by measuring your head - Spree is upfront about that. Its job starts once you have a measurement: save hats you're considering from any store into one wishlist, compare their size charts and prices side by side, and use AI Virtual Try-On on your own photo to see how a specific style actually looks on you before you order. It won't give you a size number, but it's the best way to narrow down which hat to size for in the first place.
The Bottom Line
Finding your hat size at home is a solved problem - a soft tape measure and a few minutes get you within a centimeter, which is close enough to order with real confidence. Flattening your hair first, keeping the tape snug rather than tight, and trusting the centimeter number over any single brand's letter are the quiet variables that actually matter more than which chart you use.
Once you have that number, the harder decision is usually which hat, from which store, actually looks right on you - and that's where comparing real candidates from different retailers side by side, and previewing each one on your own head with AI try-on, saves far more regret (and far fewer post-holiday exchanges) than the measuring step ever did.