Convert head circumference in cm or inches into US, UK, EU, and generic hat sizes, with adjacent-size guidance for between-size measurements.
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Convert measured head size into common hat charts Compare US, UK, EU, and generic hat sizes from a measured circumference in centimetres or inches, or start from a generic size band when that is all you have.
Input mode
Best when you have a measured head circumference from a tape measure.
Enter a measurement or pick a generic size Use a measured head circumference or select a named size band to show the closest US, UK, EU, and generic hat-size equivalents.
Hat Size Converter: US, UK, EU, and head-circumference chart guide
Hat-size conversion works best when you start from a real head measurement and only then map that measurement into the brand's published chart row. This converter turns head circumference in centimetres or inches into the closest US, UK, EU, and generic size labels, then shows the surrounding size band so you can judge whether you sit between sizes before you order.
Why head circumference is the anchor
Hat labels are only shorthand for a head-circumference range. A generic size such as M or L can be useful for quick browsing, but the more stable reference is the physical measurement around your head. That is why most hat makers tell customers to measure head circumference first and then compare that measurement with the chart for the specific brand or hat family.
Using the circumference as the anchor also reduces the usual confusion between chart systems. US and UK labels use fractional size notation, EU labels are commonly shown as the head circumference in centimetres, and generic sizes compress multiple chart rows into a wider range such as S, M, or L.
How to measure hat size properly
Use a flexible tape measure and wrap it around the head about a finger-width above the eyebrows and ears, keeping the tape level and comfortably snug rather than tight. That path usually matches where the inside sweatband of a fitted hat will sit.
If you fall between two rows, the next step depends on the style and the brand. Structured fitted caps and non-stretch dress hats often feel better when you compare the next size up if the brand says the style runs small. Softer hats, stretch fabrics, or adjustable closures may tolerate a closer fit. The converter therefore shows the adjacent generic sizes instead of pretending one label is always universally correct.
How US, UK, EU, and generic systems line up
EU hat sizing is the easiest system to read because it usually corresponds directly to the measured head circumference in centimetres. US and UK hat charts use fractional labels instead, with the UK value typically one eighth lower than the US value on the same row. Generic labels group multiple whole-centimetre rows into a broader commercial band such as XS, M, or XL.
That grouping is why a generic size result should be treated as a range rather than a promise of perfect fit. An M hat might cover two neighbouring chart rows, while an XXL or XXXL size may collapse to a single row near the top of the chart. When a brand publishes exact row-by-row measurements, the circumference row is more trustworthy than the generic label alone.
Worked example: 57 cm head circumference
A measured head circumference of 57 cm usually maps to a medium generic size, a US size 7⅛, a UK size 7, and an EU size 57. In inches that measurement is about 22.44. That is a good example of why this page shows both centimetres and inches in the result: people often measure in one unit but shop in another.
Now imagine a measurement of 57.6 cm. That falls between common 57 cm and 58 cm chart rows, so the converter still provides the nearest row but also keeps the wider generic band visible. In a rigid felt hat or a fitted cap, that is the point where checking the adjacent size can prevent an avoidable return.
What this converter does not guarantee
A hat-size chart can only tell you where the head measurement lands. It does not model crown shape, brim style, shrinkage, stretch, internal padding, hair volume, or how firmly you prefer a hat to sit. Two hats with the same nominal size can still feel different if one has a deeper sweatband or a stiffer construction.
That is why the result should be treated as a chart-matching starting point. Use it to get into the correct size family, then compare against the brand's own chart and product notes before buying, especially for fitted hats, formal felt hats, and any brand that warns its blocks run small or large.
Frequently asked questions
Should I use centimetres or inches for hat sizing?
Either works if the measurement is accurate, because both describe the same head circumference. Centimetres are often the clearest anchor because many EU charts use the measured centimetre value directly, while inches are common in US product guides. The converter shows both so you can compare across chart styles without re-measuring.
What if my head measurement falls between two hat sizes?
Treat the measured value as the anchor and then compare the adjacent size rows. If the hat is rigid, fitted, or the brand says it runs small, the larger size is often worth checking. If the hat is soft, adjustable, or intentionally close-fitting, the lower row may still be fine. The best choice depends on the brand chart and construction, not on a universal rule.
Why does the converter show a generic size band as well as a chart row?
Because generic labels such as S, M, and L usually cover more than one exact chart row. The band helps you understand the broader commercial size family, while the row tells you the closest measured chart match. Using both avoids implying that a generic label is more precise than it really is.
Can two hats with the same size label still fit differently?
Yes. Shape, material, lining, internal band design, and brand-specific blocking can all change the real fit even when the nominal size label is the same. Use the converter to narrow the likely size, then confirm the final choice with the brand's own guide and fit notes.
