{"id":66794,"date":"2026-10-13T09:12:07","date_gmt":"2026-10-13T06:12:07","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=66794"},"modified":"2026-10-13T09:12:07","modified_gmt":"2026-10-13T06:12:07","slug":"hat-size-calculator","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/beauty\/hat-size-calculator\/","title":{"rendered":"Hat Size Calculator"},"content":{"rendered":"<section class=\"not-prose calculator-box\" aria-labelledby=\"calculator-title\"><div class=\"flex items-baseline sm:items-center justify-between gap-2 sm:gap-3\"><div class=\"flex flex-col sm:flex-row sm:items-center gap-2\"><span class=\"icon icon-calculator text-primary-700! text-base! dark:text-primary-300!\" aria-hidden=\"true\"><\/span><h2 id=\"calculator-title\" class=\"text-lg font-display font-bold\">Find Your Hat Size from a Head Measurement<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"66794\" data-favorite-title=\"Hat Size\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/beauty\/hat-size-calculator\/\" data-favorite-excerpt=\"Convert your head circumference into US, UK and EU hat sizes, plus the head diameter and a general S\u2013XL category. Enter your measurement in cm or inches and pick a sizing system.\" aria-label=\"Add to Favorites\" data-favorite-icon=\"icon icon-appearance\">\n    <span class=\"icon icon-shape-star-empty\" aria-hidden=\"true\"><\/span>\n  <\/button>\n  <div class=\"calcdash-favorite__tip\" aria-hidden=\"true\">\n   <span class=\"favorite-tooltip\" id=\"favorite-tooltip\"><\/span>\n  <\/div>\n  <span class=\"sr-only\" role=\"status\" id=\"favorite-status\"><\/span>\n<\/div><\/div><form action=\"https:\/\/wpcalc.com\/en\/beauty\/hat-size-calculator\/\" method=\"POST\" class=\"calculator\" id=\"calculator-66794\" data-post=\"66794\"><fieldset class=\"fieldset-input is-1\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field has-term\" id=\"input-1\"><label for=\"field-1\">Head circumference<\/label><div class=\"term\">C<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><div class=\"field-group\"><input type=\"text\" name=\"head_circumference\" id=\"field-1\" aria-describedby=\"calc-info-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 57\" min=\"30\" max=\"80\" value=\"57\"\/><div class=\"grid grid-cols-1\"><select id=\"field-2\" name=\"unit\" aria-label=\"Unit\"><option value=\"cm\" selected>cm<\/option><option value=\"in\">in<\/option><\/select><svg class=\"pointer-events-none col-start-1 row-start-1 mr-2 size-5 self-center justify-self-end text-gray-500 sm:size-4\" viewBox=\"0 0 16 16\" fill=\"currentColor\" aria-hidden=\"true\" data-slot=\"icon\">\n              <path fill-rule=\"evenodd\" d=\"M4.22 6.22a.75.75 0 0 1 1.06 0L8 8.94l2.72-2.72a.75.75 0 1 1 1.06 1.06l-3.25 3.25a.75.75 0 0 1-1.06 0L4.22 7.28a.75.75 0 0 1 0-1.06Z\" clip-rule=\"evenodd\" \/>\n            <\/svg><\/div><\/div><small id=\"calc-info-1\">Measure around your head, about 1 cm (0.5 in) above your ears and eyebrows, where a hat would sit. Keep the tape snug but not tight.<\/small><\/div><div class=\"field\" id=\"input-2\"><label for=\"field-3\">Sizing system<\/label><div class=\"grid grid-cols-1\"><select id=\"field-3\" name=\"sizing_system\"><option value=\"us\">US (e.g. 7 1\/8)<\/option><option value=\"uk\">UK (e.g. 7)<\/option><option value=\"eu\">EU \/ metric (e.g. 57)<\/option><option value=\"all\" selected>Show all systems<\/option><\/select><svg class=\"pointer-events-none col-start-1 row-start-1 mr-2 size-5 self-center justify-self-end text-gray-500 sm:size-4\" viewBox=\"0 0 16 16\" fill=\"currentColor\" aria-hidden=\"true\" data-slot=\"icon\">\n              <path fill-rule=\"evenodd\" d=\"M4.22 6.22a.75.75 0 0 1 1.06 0L8 8.94l2.72-2.72a.75.75 0 1 1 1.06 1.06l-3.25 3.25a.75.75 0 0 1-1.06 0L4.22 7.28a.75.75 0 0 1 0-1.06Z\" clip-rule=\"evenodd\" \/>\n            <\/svg><\/div><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"66794\">Calculate<\/button><button type=\"reset\">Reset<\/button><\/div><div class=\"field is-checkbox hidden!\" id=\"field-auto-calc\"><input type=\"checkbox\" id=\"auto-calc\"><label for=\"auto-calc\">Calculate automatically<\/label><small>If enabled, the result will update automatically when you change any value.<\/small><\/div><div class=\"fieldset-result is-hidden\" aria-labelledby=\"result-title\" aria-live=\"polite\" role=\"region\"> <h3 class=\"result-title bg-gradient-to-r from-primary-50 to-gray-50 dark:from-primary-900 dark:to-gray-800\" id=\"result-title\"><span class=\"icon icon-s-pulse\" aria-hidden=\"true\"><\/span> Your Hat Size<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>US hat size<\/span><span class=\"result-term\">US<\/span><\/span><span class=\"field-value\" id=\"result-1\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result\" id=\"output-2\"><span class=\"field-title\"><span>UK hat size<\/span><span class=\"result-term\">UK<\/span><\/span><span class=\"field-value\" id=\"result-2\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result\" id=\"output-3\"><span class=\"field-title\"><span>EU \/ metric size<\/span><span class=\"result-term\">EU<\/span><\/span><span class=\"field-value\" id=\"result-3\" data-unit=\"cm\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result\" id=\"output-4\"><span class=\"field-title\"><span>Head diameter<\/span><span class=\"result-term\">d<\/span><\/span><span class=\"field-value\" id=\"result-4\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result\" id=\"output-5\"><span class=\"field-title\"><span>General size category<\/span><span class=\"result-term\">S\u2013XL<\/span><\/span><span class=\"field-value\" id=\"result-5\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><div class=\"field-result is-column\" id=\"output-6\"><span class=\"field-title\"><span>How the Sizes Were Calculated<\/span><\/span><span class=\"field-value\" id=\"result-6\"><\/span><button type=\"button\" class=\"copy-result\" data-tooltip=\"Copy Result\" aria-label=\"Copy Result\"><span class=\"copy-icon icon icon-document-copy\" aria-hidden=\"true\"><\/span><\/button><\/div><\/div><div class=\"result-actions\"><button type=\"button\" class=\"copy-link\"><svg viewBox=\"0 0 20 20\" fill=\"currentColor\" aria-hidden=\"true\"><path d=\"M12.232 4.232a2.5 2.5 0 0 1 3.536 3.536l-1.225 1.224a.75.75 0 0 0 1.061 1.06l1.224-1.224a4 4 0 0 0-5.656-5.656l-3 3a4 4 0 0 0 .225 5.865.75.75 0 0 0 .977-1.138 2.5 2.5 0 0 1-.142-3.667l3-3Z\"\/><path d=\"M11.603 7.963a.75.75 0 0 0-.977 1.138 2.5 2.5 0 0 1 .142 3.667l-3 3a2.5 2.5 0 0 1-3.536-3.536l1.225-1.224a.75.75 0 0 0-1.061-1.06l-1.224 1.224a4 4 0 1 0 5.656 5.656l3-3a4 4 0 0 0-.225-5.865Z\"\/><\/svg><span class=\"copy-link__text\">Copy link to this calculation<\/span><\/button><span class=\"sr-only\" role=\"status\" id=\"copy-link-status\"><\/span><\/div><\/div><a href=\"#respond\" class=\"hidden transition-opacity duration-300 opacity-0 w-50 text-sm justify-center items-center gap-2 px-4 py-2 rounded bg-gray-200 text-gray-700 hover:bg-gray-300\" id=\"leave-comment\"><span class=\"icon icon-comments\" aria-hidden=\"true\"><\/span>Leave a Comment<\/a><\/form><\/section><section id=\"calc-reactions\" class=\"not-prose hidden my-12 bg-gradient-to-r from-primary-50 to-gray-50 border border-indigo-100 rounded-xl px-6 py-4 shadow-sm\" data-post=\"66794\" aria-live=\"polite\" aria-labelledby=\"calc-reactions-title\"><p id=\"calc-reactions-title\" class=\"text-sm text-gray-500 text-center mb-2\">How did this result make you feel?<\/p><div role=\"group\" aria-labelledby=\"calc-reactions-title\" class=\"grid grid-cols-3 sm:flex sm:flex-row sm:justify-around gap-4 sm:items-center sm:flex-wrap\"><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"like\"><span class=\"reaction-count\" data-reaction-count=\"like\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude00 <\/span><span class=\"reaction-description font-medium\">Like <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"helpful\"><span class=\"reaction-count\" data-reaction-count=\"helpful\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\udca1 <\/span><span class=\"reaction-description font-medium\">Helpful <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"confused\"><span class=\"reaction-count\" data-reaction-count=\"confused\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude15 <\/span><span class=\"reaction-description font-medium\">Confused <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"disappointed\"><span class=\"reaction-count\" data-reaction-count=\"disappointed\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\ud83d\ude1e <\/span><span class=\"reaction-description font-medium\">Disappointed <\/span><\/button><button type=\"button\" aria-pressed=\"false\" class=\"reaction-btn flex flex-col items-center gap-1 text-sm text-gray-700 hover:text-primary-600 cursor-pointer transition-transform hover:scale-105\" data-reaction=\"inaccurate\"><span class=\"reaction-count\" data-reaction-count=\"inaccurate\">0<\/span><span class=\"reaction text-3xl\" aria-hidden=\"true\">\u274c <\/span><span class=\"reaction-description font-medium\">Inaccurate <\/span><\/button><\/div><div id=\"reaction-message\" class=\"hidden mt-8 rounded-md border border-primary-100 bg-white\/50 backdrop-blur-sm px-4 py-2 text-sm text-center shadow-sm\"><\/div><\/section><div class=\"calcdash-ad not-prose calcdash-ad--calc_result calcdash-ad--in-article\"><ins class=\"adsbygoogle\" style=\"display:block\" data-ad-client=\"ca-pub-1721569815777345\" data-ad-slot=\"6317458308\" data-ad-layout=\"in-article\" data-ad-format=\"fluid\"><\/ins><script>(adsbygoogle = window.adsbygoogle || []).push({});<\/script><\/div>\n<style id=\"wpcoderpro-inline-1\">.formula-box {\r\n\tborder-bottom: none !important;\r\n}<\/style><section class=\"formula-box\" aria-labelledby=\"formula-title\">\r\n\t<div id=\"formula-title\" class=\"not-prose font-display mb-4\"><span class=\"icon icon-formula\" aria-hidden=\"true\"><\/span><h2>Hat Size Formula<\/h2><\/div>\r\n\t<figure class=\"not-prose formula\">\r\n\t\t<figcaption class=\"formula-title\">Formula<\/figcaption>\r\n\t\t<div class=\"text-base text-gray-800\" id=\"formula\">\n\\[ d = \\frac{C}{\\pi} \\\\ \\text{US size} = \\frac{d_{\\text{in}}}{1\/8} \\text{ rounded to the nearest eighth} \\\\ \\text{UK size} = \\text{US size} - \\tfrac{1}{8} \\\\ \\text{EU size} = C \\text{ rounded to the nearest centimetre} \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(C\\) \u2014 head circumference, measured where a hat would sit<\/li>\n<li>\\(\\pi \\approx 3.14159\\) \u2014 the constant used to convert circumference to diameter<\/li>\n<li>\\(d\\) \u2014 head diameter, i.e. circumference divided by \\(\\pi\\)<\/li>\n<li>\\(d_{\\text{in}}\\) \u2014 the same diameter expressed in inches<\/li>\n<\/ul>\n<p>US hat sizes are defined as the head's diameter in inches, rounded to the nearest eighth. The UK convention is one eighth smaller, and the EU (metric) size is simply the head circumference in centimetres.<\/p>\n<p>\r\n<\/section>\n<style id=\"wpcoderpro-inline-459\">.calculation-box {\r\n\tborder-bottom: none !important;\r\n}<\/style><section id=\"calculation\" class=\"calculation-box\" aria-labelledby=\"calculation-title\">\r\n\t<div id=\"calculation-title\" class=\"not-prose font-display\"><span class=\"icon icon-unordered-list\" aria-hidden=\"true\"><\/span><h2>Hat Size \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> your head measures 57 cm around, and you want to know your hat size in every system.<\/p>\n<p>\\[ d = \\frac{C}{\\pi} = \\frac{57}{3.14159} = 18.14 \\text{ cm} = 7.14 \\text{ in} \\]<\/p>\n<p>\\[ \\text{US} = \\text{round}(7.14 \\times 8) \/ 8 = 57\/8 = 7\\tfrac{1}{8} \\]<\/p>\n<p>\\[ \\text{UK} = 7\\tfrac{1}{8} - \\tfrac{1}{8} = 7 \\quad \\text{EU} = \\text{round}(57) = 57 \\]<\/p>\n<p><strong>Result:<\/strong> US 7 1\/8, UK 7, EU 57 (head diameter 18.1 cm), general size M.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to use the calculator<\/h2>\n<ol>\n<li>Measure around your head with a soft tape, about 1 cm above your ears and eyebrows, keeping the tape snug but not tight.<\/li>\n<li>Enter the value in the <strong>Head circumference<\/strong> field.<\/li>\n<li>Choose the <strong>Unit<\/strong> of your measurement \u2014 cm or in.<\/li>\n<li>Select the <strong>Sizing system<\/strong> you need: US, UK, EU\/metric, or \"Show all systems\" to compare them side by side.<\/li>\n<li>Read your size from the results, together with the head diameter and the general S\u2013XL category.<\/li>\n<\/ol>\n<h2>What hat size means and why it matters<\/h2>\n<p>A hat that fits well stays put without pressing on your forehead or slipping over your ears. Because heads are roughly circular, hatters traditionally size hats by treating the head as a circle: the circumference you measure with a tape is converted to a diameter by dividing by \\(\\pi\\). That diameter, in inches, is the basis of the traditional US sizing system.<\/p>\n<p>The three main systems describe the same head in different units. A US size such as 7 1\/8 means the head's diameter is seven and one eighth inches. UK sizes follow the same logic but are conventionally one eighth smaller in number, so a US 7 1\/8 equals a UK 7. The EU or metric system skips the conversion entirely and uses the head circumference in centimetres \u2014 a 57 cm head takes an EU 57 hat. The letter categories (S, M, L, XL) group circumferences into broad bands: below 55 cm is S, 55\u201357 cm is M, 58\u201360 cm is L, and above 60 cm is XL.<\/p>\n<p>Knowing your size in more than one system is practical because brands label hats differently. An American maker may print \"7 1\/8\", a British maker \"7\", and a European maker \"57\" on what are essentially the same hat. With your circumference and this conversion, you can shop across all of them confidently.<\/p>\n<h2>Reference table<\/h2>\n<table>\n<thead>\n<tr>\n<th>Head circumference<\/th>\n<th>US<\/th>\n<th>UK<\/th>\n<th>EU<\/th>\n<th>Category<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>52 cm (20.5 in)<\/td>\n<td>6 1\/2<\/td>\n<td>6 3\/8<\/td>\n<td>52<\/td>\n<td>S<\/td>\n<\/tr>\n<tr>\n<td>54 cm (21.3 in)<\/td>\n<td>6 3\/4<\/td>\n<td>6 5\/8<\/td>\n<td>54<\/td>\n<td>S<\/td>\n<\/tr>\n<tr>\n<td>55 cm (21.7 in)<\/td>\n<td>6 7\/8<\/td>\n<td>6 3\/4<\/td>\n<td>55<\/td>\n<td>M<\/td>\n<\/tr>\n<tr>\n<td>57 cm (22.4 in)<\/td>\n<td>7 1\/8<\/td>\n<td>7<\/td>\n<td>57<\/td>\n<td>M<\/td>\n<\/tr>\n<tr>\n<td>59 cm (23.2 in)<\/td>\n<td>7 3\/8<\/td>\n<td>7 1\/4<\/td>\n<td>59<\/td>\n<td>L<\/td>\n<\/tr>\n<tr>\n<td>61 cm (24.0 in)<\/td>\n<td>7 5\/8<\/td>\n<td>7 1\/2<\/td>\n<td>61<\/td>\n<td>L<\/td>\n<\/tr>\n<tr>\n<td>63 cm (24.8 in)<\/td>\n<td>7 7\/8<\/td>\n<td>7 3\/4<\/td>\n<td>63<\/td>\n<td>XL<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Assumptions, limitations and practical tips<\/h2>\n<ul>\n<li><strong>The calculator assumes a roughly circular head.<\/strong> Real heads are slightly oval, so the diameter derived from \\(\\pi\\) is an equivalent circle, not an anatomical measurement. This is exactly how traditional hat sizing works, so the result matches standard size charts.<\/li>\n<li><strong>Sizing conventions vary between manufacturers.<\/strong> One brand's 7 1\/8 may fit differently from another's. Use the calculated size as a starting point and check the maker's own chart before buying, especially for fitted caps and dress hats.<\/li>\n<li><strong>Measure carefully.<\/strong> Take two or three readings to be consistent, and measure snugly against the head \u2014 thick hair or a ponytail can add a centimetre or more. If you are between sizes, most hatters recommend going up and tightening the fit with sizing tape or foam strips inside the sweatband.<\/li>\n<li><strong>Materials matter.<\/strong> Wool felt and straw hats stretch and conform slightly over time; stiff structured caps do not, so precision matters more for the latter.<\/li>\n<\/ul>\n<p>If you track other body measurements \u2014 for example with our <a href=\"https:\/\/wpcalc.com\/en\/beauty\/a-body-shape-index-calculator\/\">A Body Shape Index calculator<\/a> or the <a href=\"https:\/\/wpcalc.com\/en\/beauty\/hair-density-calculator\/\">Hair Density calculator<\/a> \u2014 you can note your head circumference alongside them for future reference.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Convert your head circumference into US, UK and EU hat sizes, plus the head diameter and a general S\u2013XL category. Enter your measurement in cm or inches and pick a sizing system.<\/p>\n","protected":false},"author":3168,"featured_media":0,"comment_status":"open","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[2],"tags":[12],"class_list":["post-66794","post","type-post","status-publish","format-standard","hentry","category-beauty","tag-appearance"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66794","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/users\/3168"}],"replies":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/comments?post=66794"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66794\/revisions"}],"predecessor-version":[{"id":66795,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66794\/revisions\/66795"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=66794"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=66794"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=66794"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}