Hat Size Chart: Complete Guide (US, UK, EU, cm & inches)

The one hat sizing chart that reconciles US, UK, EU, cm and inches — plus how to read fractional sizes like 7 5/8, what a fitted cap number really means, and what to do when you're between sizes.

Published 2026-03-18 · 8 min read

Marek Cieśla

Founder, Woolet Eyewear · Serial entrepreneur · LinkedIn

Last updated: August 2026

Hat sizing is one of the last places in fashion where four different measurement systems are still in daily use — cm, inches, fractional US sizes, and letter sizes — and nobody at the shop counter agrees on the conversion. This is the single chart that reconciles all four, plus the context you need to read it correctly the first time.

One more thing the chart will tell you, if you know where to look: your hat size is the single best off-the-shelf predictor of whether glasses will fit you. The two measurements sit on the same ring of your skull. Skip to the hat size → glasses size conversion ↓

The rule that fixes 90% of confusion

Every hat size in the world is derived from one number: your head circumference in centimetres. US, UK and EU sizes are just three different ways of labelling the same measurement. Get the cm right and the rest is arithmetic.

The Master Hat Size Chart

Read across the row. If your circumference lands between two rows, use the larger one — see between sizes below. Don't know your circumference yet? Measure your head in 60 seconds.

Head (cm)	Head (in)	US	UK	EU / cm	Letter	Temple width*
53	20⅞	6⅝	6½	53	XXS	146 mm
54	21¼	6¾	6⅝	54	XS	148 mm
55	21⅝	6⅞	6¾	55	S	150 mm
56	22	7	6⅞	56	S / M	151 mm
57	22⅜	7⅛	7	57	M	153 mm
58	22¾	7¼	7⅛	58	M	155 mm
59	23¼	7⅜	7¼	59	L	157 mm
60	23⅝	7½	7⅜	60	L / XL	159 mm
61	24	7⅝	7½	61	XL	161 mm
62	24⅜	7¾	7⅝	62	XL	163 mm
63	24¾	7⅞	7¾	63	XXL	~165 mm
64	25¼	8	7⅞	64	XXL	~167 mm
65	25⅝	8⅛	8	65	XXXL	~169 mm
66	26	8¼	8⅛	66	XXXL	~171 mm

*Temple width = distance across the widest point of your skull, where glasses arms sit. Median values from ANSUR II (n = 4,082 men); 63 cm and above are extrapolated. Rows highlighted in cream (58 cm+, US 7¼ and up) are where mainstream hats and mainstream eyewear both start running out — see the conversion table below.

Your Hat Size Predicts Your Glasses Size

Hat size is a circumference. Glasses size is a breadth. They are not the same measurement — but they are measured on the same ring of your skull, roughly a centimetre above your ears, and they move together. In the ANSUR II anthropometric survey (n = 4,082 men) the two correlate at r = 0.55, tight enough that your hat size narrows your frame width to a 4 mm window before you try anything on.

The arithmetic, if you want it: temple width (mm) ≈ 1.91 × head circumference (cm) + 44.7

Hat size (US)	Head (cm)	Your temple width	Frame front width you need	In mainstream frames
6⅝ – 6⅞	53 – 55	146 – 150 mm	140 – 148 mm	Standard sizes fit. You are in the range every brand designs for.
7 – 7⅛	56 – 57	151 – 153 mm	148 – 152 mm	Borderline. Look for models labelled “wide” or “XL” — regular fits leave marks after a few hours.
7¼ – 7⅜	58 – 59	155 – 157 mm	155 – 158 mm	They pinch. 93% of men this size are already past the point where mainstream frames stop.
7½ – 7⅝	60 – 61	159 – 161 mm	158 – 162 mm	Nothing off the shelf fits. Arms splay outward, the front bows, lenses sit off-axis.
7¾ and up	62+	163 mm+	162 mm+	Bespoke territory. The same shops that stock your hat size do not exist in eyewear.

Frame front width = total width of the frame, hinge to hinge — not lens width. It is the number that decides whether the arms run straight back or splay. Most mainstream brands top out around 148 mm; a handful of “XL” lines reach 152 mm.

Where Woolet sits on this table

We build one front width: 158 mm. That is deliberate — it covers the 58–61 cm band (US 7¼ to 7⅝) properly rather than covering everything badly.

If your hat is 7 or smaller, you do not need us. A mainstream frame labelled “wide” or “XL” will fit you, and we would rather tell you that than sell you 158 mm you will have to push back up your nose. If you are 62 cm and above, 158 mm is still short for you — that is what bespoke is for.

See the 158 mm frames → · Bespoke up to 162 mm →

The line to remember: 7¼. Not 7½. A US 7¼ hat means a 58 cm head, and at 58 cm the median temple width is already 155 mm — seven millimetres past where most eyewear brands stop designing. If you have ever bought a hat in 7¼ or larger and separately assumed your glasses were “just a bit tight”, those are the same fact.

Don't want to estimate from a hat size?

The table above gives you a median. Your own face can sit 4–5 mm either side of it. Woolet's AI Fit Wizard measures your actual temple width from a single phone photo — accurate to about 2 mm, using a credit card as the reference object. No tape measure, no guessing which side of the median you are on.

Measure my temple width → · See frames at 158 mm →

How to Read US Fractional Sizes (7, 7⅛, 7¼…)

The US size is not arbitrary — it's the hat's internal diameter in inches, assuming the head is a perfect circle. To convert from any circumference:

US size = head circumference (in) ÷ π (≈ 3.1416)

A 60 cm head is 23.62 in ÷ 3.1416 = 7.52 → rounded to the nearest eighth = 7½. That's why the chart moves in 1/8-inch increments: it mirrors the way felt hat blocks and fitted-cap moulds are actually manufactured.

UK vs US: The 1/8 Shift

UK sizes label the same physical hat one-eighth of an inch smaller than the US number. Nobody outside the trade knows why — it's a leftover from parallel 19th-century hatter guilds — but the shift is exact and predictable. If a British brand tells you the hat is a 7⅜, the American equivalent is 7½.

EU and Continental Sizing

Europe skipped the fractions and simply uses the head circumference in cm as the size. A "60" hat fits a 60 cm head. This is by far the least ambiguous system — and the reason so many premium Italian and French hatmakers (Borsalino, Maison Michel, Christys' London for EU markets) label in cm directly.

Fitted Cap Sizing (New Era, 59FIFTY)

Baseball fitted caps use US fractional sizing but with tighter production tolerances than felt hats. The typical New Era 59FIFTY size range is 6¾ to 8 (54–64 cm). Above 8, you're into specialist territory — Mammoth Headwear, Big Hat Store, and a small number of Etsy makers cover 8⅛ (65 cm) and up.

A fitted cap runs about 3–5 mm tighter than a felt hat at the same labelled size, because the polyester/wool shell has less give than a stretched-and-blocked felt crown. If you're between sizes on a fitted cap, size up.

What to Do When You're Between Sizes

Size up, then pad. A self-adhesive hat sizing strip (also called "hat size reducer" — costs about $3) takes 60 seconds to install and reduces internal circumference by 3–6 mm. That's the width of a full half-size.
Never stretch more than 3–4 mm. Steaming a felt hat can gain about a quarter-inch. Beyond that the crown deforms permanently and the sweatband tears.
Watch for the "red ring" test. If you wear the hat for 20 minutes and it leaves a visible mark across your forehead, it's undersized by at least a half-size — return it, don't stretch it.

Head Shape Matters (Not Just Size)

Two people with identical 60 cm circumferences can wear the same labelled size and get completely different fits. Circumference sets the size; shape decides the comfort.

Oval (long front-to-back). The default Western pattern — most brands are cut for it.
Round (nearly circular from above). Common in East Asian and some Central-European populations. A standard oval hat pinches at the temples and gaps at the front and back. Stetson, Bailey and Christys' London label round-fit and long-oval variants explicitly.

If your hats always pinch at the sides even in the correct size, your head is round, not big. That's a shape problem, not a sizing problem — and no chart will fix it.

The Bigger Picture: This Is Not a Rare Problem

The eyewear industry designs as if large heads were an edge case. The anthropometry says otherwise. In ANSUR II, 36.8% of men measure 58 cm or more — a US 7¼ hat — and 93% of them have a temple width above 148 mm, past the point where most frame ranges stop. Above 60 cm (US 7½) it is 6.4% of men, and there the figure is 99%. Among women, 30.6% measure 57 cm or more.

So it is not that a handful of unusually large people struggle to buy glasses. It is that roughly a third of adult men are being fitted from a size range that was never cut for them, and have quietly decided the marks behind their ears are normal. Hat retail solved this decades ago — that is why XL and XXL exist on the shelf, and why the specialist shops linked above have a business. Eyewear never did.

That is the gap Woolet was built to fill: frames engineered from the front width outward, starting at 158 mm and going up to 162 mm bespoke — for exactly the crowd that shops for hats in XL and XXL.

For the same crowd

If your hat size is 7¼ or larger, mainstream frames are pinching your temples whether or not you have noticed. Woolet 007 and 009 ship at 158 mm front width, in Italian Mazzucchelli acetate, hand made in EU.

Glasses for big heads → · Bespoke up to 162 mm →

Hat Size and Glasses Size: Common Questions

What size glasses do I need for a 7⅝ hat?

A US 7⅝ hat is a 61 cm head, which puts your temple width around 161 mm. You need a frame with a front width of roughly 158–162 mm. Standard frames run 140–148 mm, so nothing off the shelf will sit straight on you.

Does a big head always mean a wide face?

Not always, but usually. Head circumference and head breadth correlate at r = 0.55 in ANSUR II — strong, not absolute. A long-oval head can carry a 60 cm circumference with a narrower-than-median breadth. That is the 4–5 mm of uncertainty the table above cannot remove; a photo measurement can.

Is temple width the same as face width?

No. Face width is usually quoted as cheekbone-to-cheekbone (bizygomatic breadth), which runs about 12–14 mm narrower than temple width. Frames sit on the temples, not the cheekbones, so temple width is the number that decides fit.

My hat is 7½ but my glasses feel fine. Am I wrong?

Check for the marks, not the feeling. Pressure that builds over hours reads as normal because it is constant. If you have indentations in front of your ears after a working day, or the arms have visibly splayed outward over time, the frame is too narrow regardless of how it felt in the shop.

Where do these numbers come from?

ANSUR II, the 2012 U.S. Army anthropometric survey — 4,082 men and 1,986 women, each measured for both head circumference and head breadth by trained anthropometrists. It is the largest public dataset with both measurements on the same subject. The sample is military and therefore younger and fitter than the general population; head dimensions are less affected by this than body dimensions, but treat the medians as close estimates rather than exact population values.

Quick Reference: Common Conversions

7 hat size in cm — 56 cm (22 in)
7¼ hat size in cm — 58 cm (22¾ in)
7½ hat size in cm — 60 cm (23⅝ in)
7 5/8 hat size in cm — 61 cm (24 in)
7¾ hat size in cm — 62 cm (24⅜ in)
7⅞ hat size in cm — 63 cm (24¾ in)
Size 8 hat in cm — 64 cm (25¼ in)