Body Shape Styling
Size & Fit
Hat Size Calculator: Inches, Centimetres and Fitted Sizes
Hat sizing confuses people for a reason that almost no chart explains: the number on a fitted hat is not a measurement of anything you can find with a tape. A size 7 hat does not have a seven inch anything. The number is your head's circumference divided by pi, a convention inherited from the days when hatters worked from wooden blocks. This hat size calculator takes the measurement you can actually take — the distance around your head — and returns the fitted size, the European centimetre size, the UK size and the letter size together. It also covers the part the charts leave out entirely, which is that two people with identical measurements can need different hats, because heads are not all the same shape.
Short answer: A 58 cm head is a US 7¼, a UK 7⅛, an EU 58 and a medium. Divide your head circumference in inches by 3.14 to get the fitted size, or read the chart below — every row gives both units.
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Last reviewed September 2026
Hat Size Calculator: Inches, Centimetres and Fitted Sizes Conversion Chart
Interactive converter requires JavaScript. You can view the full reference table below.
View Size Chart Below ↓Results are approximate and sizes vary by brand. Check the brand's own chart before buying — see our accuracy note.
This hat size chart converts between every system in ordinary use. Read the circumference columns first, because those are the only figures you can measure on yourself — everything else is derived from them. The US fitted size is the circumference in inches divided by pi, which is why it lands on eighths rather than on whole numbers. The European size is simply the circumference in centimetres, making it the most readable system of the four. UK sizes run one eighth below US sizes for the same head, a difference small enough to be easy to miss and large enough to matter in a structured hat.
Between two rows? Round up. A hat that is slightly large can be sized down with a foam sizing tape; one that is too small cannot be made bigger.
Short answer:
The fitted hat size is your head circumference in inches divided by pi. A 23⅞ inch head divided by 3.14 is 7.6, which is written as 7⅝. The number is not a measurement of your head — it is the diameter of the circle your head would be if it were perfectly round.
There is a thread on the hats forum titled, roughly, that American inch hat sizing makes no sense. It is a fair complaint, and the explanation is genuinely strange. Hatters have worked from oval wooden blocks for centuries, and those blocks were described by their diameter rather than by the distance around them. So when sizing was formalised, the number that stuck was the diameter — circumference divided by pi — rather than the circumference itself. That is why fitted hats come in eighths, and why a hat size in cm and a hat size in inches look like numbers from two different planets. A 61 cm hat is a 7⅝, and nothing about those two figures suggests they describe the same head.
Once you know the rule, the whole system becomes arithmetic you can do in your head. Divide inches by roughly 3.14 and round to the nearest eighth. Going the other way, multiply the fitted size by 3.14 for inches, or by about 8 for centimetres. A 7½ is 23½ inches or 60 centimetres. A 7⅛ is 22⅜ inches or 57 centimetres. Each eighth of a size is about half an inch of circumference, or a little over a centimetre — which is why a single eighth is the difference between a hat that sits and one that slides.
European sizing sidesteps the whole problem by using the circumference in centimetres as the size, exactly as European ring sizes do. An EU 58 hat fits a 58 centimetre head. If you are buying from a European maker and have your measurement in centimetres, there is nothing to convert at all. The conversion only becomes necessary going into the American or British systems, and the table below does that for every eighth in common production.
One eighth of a size is about 1.3 centimetres of circumference. That is the entire difference between two neighbouring sizes.
Tape sits ~1 cm above eyebrows and directly over ears.
Short answer:
Run a tape measure around your head just above the ears and across the middle of your forehead, where a hat would naturally sit. Keep it snug but not tight. That figure is your head circumference, and every hat size on this page comes from it.
A hat sits above the ears and across the middle of the forehead, roughly a centimetre above the eyebrows. That is the line to measure, not the widest point of your skull and not around the hairline. Measure too high and every hat you buy will be loose; too low and nothing will go on.
Hold the tape level all the way round and pull it until it sits against your head without compressing. If you can slide a finger underneath without effort, it is too loose. Take the reading in centimetres if you can — European sizing uses that figure directly, so it saves a conversion.
If you wear your hair up, down, braided or in a bun under hats, measure with your hair that way. The difference is frequently a full size. Measure two or three times and use the largest reading, since the tape tends to sit slightly high on the first attempt.
No tape measure? Use a strip of paper or a shoelace, mark the overlap, then lay it flat against a ruler. It is the same method as measuring a ring, and it is just as accurate.
Round up and use a foam sizing tape inside the sweatband. They cost very little, come in several thicknesses, and are how hat shops have fitted between-size customers for a century. There is no equivalent trick for a hat that is too small.
Short answer:
Heads come in three broad oval shapes — long oval, regular oval and round oval. A hat in the correct size will still fit badly if it is blocked for a different shape. If a hat feels tight front to back but loose at the sides, you have a long oval head and the hat is a round oval.
Head circumference tells you how much hat you need. It does not tell you what shape that hat should be, and heads vary more in shape than most people realise. A long oval head is noticeably deeper front to back than it is wide. A round oval is closer to circular. A regular oval sits between them, which is what most mass-market hats are blocked for, and which is why most mass-market hats fit most people acceptably and nobody perfectly.
The symptoms are specific and easy to recognise once you know them. A hat that pinches at the forehead and the back of the head while gaping above the ears is too round for you. A hat that grips at the sides and leaves a gap at the front is too long. In both cases the size is correct — the shape is not, and no amount of sizing up will fix it, because sizing up simply makes the wrong shape bigger.
Structured hats show this most: fitted caps, fedoras, boaters and cowboy hats are all blocked to a shape and hold it. Soft hats forgive almost everything, which is why a beret, a beanie or a bucket hat will sit on any head at the right size. If you have struggled with structured hats and assumed you were between sizes, shape is the more likely explanation, and a good hatter can steam a hat to your shape in a few minutes.
Long oval · deeper front to back · pinches at the forehead in a round hat
Regular oval · what most hats are blocked for
Round oval · wider side to side · gaps at the front in a long hat
Same circumference. Three different hats.
Short answer:
Cowboy hats use the same fitted size numbers as any other hat — a 58 cm head is a 7¼. What differs is the fit: western hats are meant to sit firmly and are shaped to the wearer, so they are bought snug rather than comfortable and steamed to fit afterwards.
A cowboy hat size chart looks identical to any other hat chart, because it is. The numbers are the same fitted sizes derived the same way. The difference is in what a correct fit feels like. A western hat is expected to stay on through wind, movement and a vehicle door, so it is fitted more firmly than a fedora or a cap — snug enough to leave a faint line on the forehead after an hour, without giving you a headache.
The second difference is that felt western hats are shaped, not just sized. A hatter will steam the crown and brim to your head and to the shape you want, and a good quality felt hat can be reshaped repeatedly over its life. This is why western retailers push so hard on buying in person: the size gets you to the right hat, and the steaming makes it yours. It is also why an oval-shaped head is far less of a problem in western hats than in fitted caps — the hat is adjusted to you rather than the reverse.
For buying online, the practical rules are straightforward. Order your measured size rather than sizing up. Expect a new felt hat to feel firmer than you think is right, because it will relax slightly with wear. And check whether the maker uses standard fitted sizes or its own S/M/L scale, since western brands are split between the two and the S/M/L versions vary noticeably between houses.
Short answer:
Structured hats need an exact size. Soft hats do not. A fitted cap or a fedora has to be right to the eighth; a beret, beanie or bucket hat will sit happily a size either way.
Not every hat needs the same precision, and knowing which ones do saves a great deal of returning. The table below is what our calculator uses when you select a hat type, and it is the reason the guidance line under your result changes depending on what you are buying.
Snapbacks and adjustable caps are not in this table because they have no size — they run roughly 55 to 61 centimetres and adjust within that range.
Short answer:
Head size is not gendered — a 58 cm head is a 7¼ whoever it belongs to. What differs is the labelling. Women's hats are frequently sold as S/M/L or one-size-fits-most with an internal band, while men's hats are sold in numbered fitted sizes.
There is no such thing as a women's head measurement, and a women's hat size chart is not a separate scale. It is the same circumference converted the same way. The genuine difference is commercial: women's millinery and fashion hats have long been sold in letter sizes or as one-size-fits-most, while men's hats kept the numbered fitted convention from the hatters. Average measurements do differ a little between the two markets, which is why a women's medium and a men's medium are not always the same centimetre range, but the arithmetic underneath is identical.
One-size-fits-most is the part worth understanding before you buy. It usually means the hat is blocked at around 57 to 58 centimetres with an elasticated or adjustable inner band that gives an extra centimetre or two. If you measure above 59, one-size will be tight, and if you measure below 55 it will sit low no matter what the band does. Either way, the measurement tells you before the hat arrives, which is the entire point of taking it.
Hair changes the answer here more than anywhere else. A hat bought to fit over loose hair will be loose over a sleek style, and a hat fitted to a bun will not go on otherwise. If you wear your hair several different ways, measure both extremes and buy for the larger, then use a sizing tape for the smaller.
Letter ranges vary between brands by a centimetre or so. Where a maker publishes its own chart, that chart wins.
Short answer:
Fitted cap makers run close to standard. Fashion and sun-hat brands vary widely because many use their own letter scales rather than fitted sizes.
Every number on this page assumes a maker cuts to the standard scale, and in hats that assumption holds better than in clothing — the circumference is a physical fact. Where brands diverge is in the shape they block to and in whether they use fitted sizes at all. The table below records both, and is reviewed quarterly.
Reviewed quarterly. Last updated September 2026. Where a maker publishes its own chart, use it — this table describes the direction of drift, not a replacement for the brand's own measurements.
Step-by-step instructions with photos and a printable guide.
How sizing varies for caps, berets, bucket hats, fedoras and more.
How to adjust a hat that is slightly large and what to do if it is tight.
Hat sizing has a genuine formula behind it, which makes it unusual among the size systems on this site. Here is the formula and where it stops being enough.
The fitted size is the head circumference in inches divided by pi, rounded to the nearest eighth — the same derivation hatters have used since blocks were described by diameter. The European size is the circumference in centimetres, used directly with no conversion. UK sizes sit one eighth below US sizes for the same head, a convention that has held since the two trades diverged. Letter sizes are ranges rather than points, and because they vary between makers we give the centimetre range each letter covers rather than a single equivalent. Every row in the chart is calculated from the formula and cross-checked against the published charts of the ten makers in the table above.
Because it is the only one that determines whether a hat goes on. Head length, width and crown height all affect how a hat looks and how it sits, but none of them changes the size you order. Asking for them would imply a precision the size system does not have. The shape question matters enormously and is covered in its own section, but it is a question of which hat to choose, not which number to order.
Three situations. Brands using their own letter scales, where a medium may cover a different range than the one here and the maker's chart is the only authority. Heads that are markedly long or round oval, where the correct size can still fit badly and the fix is shape rather than number. And anything knitted or adjustable, where the size is a range and the calculation is close to meaningless. In all three, the measurement is still worth having — it just needs to be read against the specific hat rather than against a general chart.
For a plain conversion reference with no commercial interest attached, Baruch College publishes a hat conversion chart for its commencement regalia that has become one of the most widely used tables online. For the trade's own account of sizing, Lock and Co Hatters, who have been fitting hats in London since 1676, publish a sizing guide that explains the British convention from the inside.
FULL CHART
Hat Size Chart: US, UK, EU and Letter Sizes
✎
7¼ = 58 cm
7⅝ = 61 cm
22 in = size 7
THE PART NOBODY EXPLAINS
Why Hat Sizes Are Fractions Like 7⅝
Fitted size to centimetres
6¾
54 cm
6⅞
55 cm
7
56 cm
7⅛
57 cm
7¼
58 cm
7⅜
59 cm
7½
60 cm
7⅝
61 cm
7¾
62 cm
7⅞
63 cm
8
64 cm
QUICK LOOKUP
Most searched
7⅛=57 cm
7¼=58 cm
7⅜=59 cm
7½=60 cm
7⅝=61 cm
7¾=62 cm
BEFORE YOU CALCULATE
How to Measure Hat Size at Home
01 Find the line the hat will sit on
02 Measure snug, not tight
03 Measure the way you will wear it
If you are between sizes
THE OTHER HALF OF FIT
Your Head Shape Matters as Much as Your Head Size
WESTERN
Cowboy Hat Size Chart and How Western Sizing Differs
BY HAT TYPE
How Much the Size Matters, by Hat Type
TWO CONVENTIONS
Women's Hat Size Chart and Why It Looks Different
BRAND BY BRAND
Which Hat Brands Run Small, Large or True
Measure Your Head Size
Find the Right Size for Your Hat
Get a Better Fit
METHODOLOGY
How This Calculator Works
What this hat size calculator is built on
Why circumference is the only measurement we ask for
Where this calculator is least reliable
Written & researched by Md Zubayer Al Hasan
Last reviewed September 2026
7 years in garment manufacturing · Sizing & grading specialist
QUESTIONS
Hat Size Calculator FAQ
- What hat size is 58 cm?
- A 58 cm head is a US fitted 7¼, a UK 7⅛, an EU 58 and a medium in letter sizing. In inches that is a circumference of about 22¾.
- What is 7⅝ in centimetres?
- A 7⅝ hat fits a head of about 61 centimetres, or 23⅞ inches. Multiply any fitted size by roughly 8 for the centimetre equivalent, or by 3.14 for inches.
- Why are hat sizes written as fractions?
- Because the fitted size is the circumference divided by pi, a convention from when hatters described their wooden blocks by diameter. Dividing by 3.14 rarely produces a whole number, so sizes land on eighths.
- How do I measure my hat size without a tape measure?
- Wrap a strip of paper or a shoelace around your head where a hat would sit, mark the overlap, then lay it flat against a ruler. It is as accurate as a tape, and paper is better than string because it does not stretch.
- What hat size am I if I am between two sizes?
- Round up. A hat that is slightly large can be reduced with a foam sizing tape inside the sweatband, which costs very little. A hat that is too small cannot be made bigger, apart from a limited stretch on felt by a hatter.
- Are women's and men's hat sizes different?
- The measurements are not. A 58 cm head is a 7¼ regardless. What differs is labelling: women's hats are often sold in letter sizes or one-size-fits-most, men's in numbered fitted sizes. Average measurements differ slightly between the two markets, but the conversion is identical.
- Do UK and US hat sizes match?
- No. UK sizes run one eighth below US sizes for the same head, so a US 7¼ is a UK 7⅛. It is a small difference that is easy to overlook and enough to matter in a structured hat.
- What if my hat is the right size but still fits badly?
- It is probably the wrong shape rather than the wrong size. Heads are long oval, regular oval or round oval, and a hat blocked for one will pinch or gape on another. Sizing up makes the wrong shape bigger rather than fixing it.