How to Measure Your Head for a Hat (Free Method + Size Chart in cm & inches)

Measure your head circumference at home in 60 seconds and find your true hat size — no tape measure required. A no-nonsense guide built for bigger heads (7¾ and up).

Published 2026-03-15 · 7 min read

Marek Cieśla

Founder, Woolet Eyewear · Serial entrepreneur · LinkedIn

Last updated: March 2026

If you've ever bought a hat that gave you a red ring across your forehead by lunchtime, the problem was never your head. It was the number on the label. Hat sizing is one of the last corners of fashion still trapped in three parallel systems — inches, centimetres, and letter sizes that mean something different at every brand — and almost nobody teaches you the one measurement that decides all of them.

This guide fixes that in about a minute. No specialist tools, no visit to a hatter, no returning three sizes in a row. Just a string, a ruler, and the chart below.

The one number that matters

Your head circumference — measured in centimetres around the widest part of your skull, roughly 2.5 cm above your eyebrows and ears. Every hat size in every country converts directly from this single number. Get it right once and you never guess a size again.

How to Measure Your Head in 60 Seconds

You need one flexible thing long enough to wrap around your head — a piece of string, a shoelace, a phone charging cable, a strip of paper — and something to measure it against. A ruler is ideal, but a credit card works too (every credit card in the world is exactly 85.6 mm wide, by ISO/IEC 7810 standard).

Find the line. Place your fingers about 2.5 cm (1 inch) above your eyebrows in front, and just above the tops of your ears on the sides. That's where a hat brim sits — and the widest part of your skull.
Wrap the string. Loop it once around your head along that exact line. Keep it level — no dipping at the back — and snug, not tight. If it presses into your skin, loosen it slightly.
Mark the overlap. Pinch the point where the string meets its own end, or mark it with a pen.
Measure it flat. Lay the string next to a ruler and read the length in centimetres. No ruler? Line it up against credit cards edge-to-edge: each card is 8.56 cm, so 7 cards ≈ 60 cm.
Round up. If you land between two sizes, always go up. A hat can be padded down with a sizing strip; it cannot be stretched up by a full size without deforming.

Shortcut: measure with your phone

Woolet built an AI Fit Wizard that measures your face width from a single phone photo using a credit card as a reference — accurate to about 2 mm. Face width and head circumference correlate strongly (bigger head, wider face, almost always), so the Fit Wizard gives you a solid estimate of both in about 30 seconds.

Try the AI Fit Wizard →

Hat Size Chart: cm, inches, US, UK, EU

Match your measurement to the row below. This chart uses the international standard hat sizing conversion — the same numbers your hatter, your fitted-cap brand, and your cowboy-hat maker are all working from, whether they say so or not.

Head (cm)	Head (in)	US	UK	EU	Letter
54	21¼	6¾	6⅝	54	XS
55	21⅝	6⅞	6¾	55	S
56	22	7	6⅞	56	S
57	22⅜	7⅛	7	57	M
58	22¾	7¼	7⅛	58	M
59	23¼	7⅜	7¼	59	L
60	23⅝	7½	7⅜	60	L / XL
61	24	7⅝	7½	61	XL
62	24⅜	7¾	7⅝	62	XL
63	24¾	7⅞	7¾	63	XXL
64	25¼	8	7⅞	64	XXL
65	25⅝	8⅛	8	65	XXXL

Rows highlighted in cream are the sizes most mainstream brands don't stock — the reason bigger heads have to shop specialist.

What Counts as a "Big Head" for Hats?

The short answer: anything above 60 cm (US 7½). The average adult male head measures 56–58 cm; the average adult female head measures 54–56 cm. From about 60 cm upward, you leave the range that most off-the-shelf brands actually stock — Zara, H&M and most fashion caps stop at "one size fits most", which in practice means up to about 59 cm.

For heads above 61 cm, you're looking at specialist brands: Mammoth Headwear, Big Hat Store, and Noggin Boss are the three most-cited names for XL and XXL fits. If you consistently wear 7¾ or 8, one-size caps and vintage fedoras are simply not built for you — and no amount of steaming will fix that.

The Overlap Nobody Talks About: Big Head, Wide Face

Head circumference and face width aren't the same measurement, but they track together closely. In our own fitting data, roughly 4 out of 5 customers with a head above 60 cm also measure above 150 mm across the temples — which puts them outside the sizing range of virtually every mainstream eyewear brand.

If your hats never fit, your glasses probably don't either. The same standard bell curve that stops at 60 cm on hats stops at 145 mm on eyewear. That's the gap Woolet was built to fill — frames that start at 158 mm front width, designed specifically for faces the mainstream industry sizes out.

Related: eyewear for the same crowd

If your hat size is 7½ or up, there's a strong chance mainstream frames pinch your temples too. Woolet 007 and 009 ship at 158 mm front width — built for exactly this group.

See glasses for big heads → · Measure your face width →

Common Mistakes When Measuring

Measuring too high. The tape should sit about 2.5 cm above the eyebrows — not on the hairline. Measuring at the hairline underestimates by 1–2 cm and drops you a full size.
Pulling the string tight. Snug, not tight. A hat has to sit comfortably for hours; a tape pulled hard gives you a size that will squeeze after 20 minutes.
Not keeping it level. If the string dips at the back of your skull, the reading is wrong. Use a mirror to check.
Measuring once. Do it three times and take the middle number. Skin, hair volume and how tightly you hold the string all shift the reading by 3–5 mm.
Rounding down. If you're between sizes, always go up. A padded strip inside a hat is a 30-second fix; a hat that's a size too small is a return.

How Hat Shape Changes the Fit

Head circumference decides size, but two heads at 60 cm can wear the same size and get completely different results — because human skulls aren't perfect circles. The two shapes that matter:

Oval (long front-to-back). The most common Western shape. Standard hat blocks are built for this — most brands work fine.
Round (nearly circular from above). More common in East Asian and some Central-European populations. A standard oval hat will pinch at the temples and gap at the front and back. Look for brands that offer a "round oval" or "long oval" fit — Stetson, Bailey, and Christys' London all label them.

If your hats always pinch at the sides even in the right circumference, your head is round — not big. Different problem, different fix.

Quick Answers

What size hat is 58 cm? US 7¼, UK 7⅛, EU 58, letter size M.

What size hat is 60 cm? US 7½, UK 7⅜, EU 60, letter size L/XL — the tipping point where mainstream brands stop stocking.

Is 62 cm a big head? Yes. That's US 7¾, XL, and above the range of most off-the-shelf caps. You need a specialist brand.

How do I know if a hat is too small? If it leaves a red ring on your forehead after 30 minutes, or you feel a headache building at the temples, it's undersized by at least a half-size. Return it.

More on fit for bigger heads and wider faces: best glasses for big heads · what size glasses for a large head · how to measure your face width · try the AI Fit Wizard.