{"id":57711,"date":"2016-03-17T18:09:53","date_gmt":"2016-03-17T16:09:53","guid":{"rendered":"http:\/\/wpcalc.com\/?p=57711"},"modified":"2026-09-28T13:51:16","modified_gmt":"2026-09-28T10:51:16","slug":"crown-rump-length","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/pregnancy-baby\/crown-rump-length\/","title":{"rendered":"Crown Rump Length (CRL) 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\">Fetal Length by Gestational Week Calculator<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"57711\" data-favorite-title=\"Crown Rump Length (CRL)\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/pregnancy-baby\/crown-rump-length\/\" data-favorite-excerpt=\"Estimate crown\u2013rump length from a gestational age of 6 to 14 weeks. Enter the number of weeks and choose millimeters or centimeters.\" aria-label=\"Add to Favorites\" data-favorite-icon=\"icon icon-embryo\">\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\/pregnancy-baby\/crown-rump-length\/\" method=\"POST\" class=\"calculator\" id=\"calculator-57711\" data-post=\"57711\"><fieldset class=\"fieldset-input\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field\" id=\"input-1\"><label for=\"field-1\">Number of weeks<\/label><input type=\"text\" name=\"number_of_weeks\" id=\"field-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"6\" max=\"14\" value=\"10\"\/><\/div><div class=\"field\" id=\"input-2\"><label for=\"field-2\">Unit<\/label><div class=\"grid grid-cols-1\"><select id=\"field-2\" name=\"unit\"><option value=\"mm\">mm<\/option><option value=\"cm\">cm<\/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=\"57711\">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 Results<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>Crown Rump Length<\/span><span class=\"result-term\">length<\/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><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=\"57711\" 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\">2<\/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\">1<\/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>Crown Rump Length (CRL) 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\\[i=\\left\\lfloor 2(w-6)\\right\\rfloor,\\qquad \\mathrm{CRL}_{\\mathrm{cm}}=c_i,\\qquad \\mathrm{CRL}_{\\mathrm{mm}}=10c_i\\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(w\\) \u2014 gestational age in weeks, from 6 to 14.<\/li>\n<li>\\(i\\) \u2014 the index of the most recent half-week entry, starting at 0 for 6 weeks.<\/li>\n<li>\\(c_i\\) \u2014 the crown\u2013rump length in centimeters at that entry, as listed in the reference table below.<\/li>\n<\/ul>\n<p>The calculator uses a fixed lookup table rather than a continuous growth formula. For an age between two half-week entries, it uses the earlier entry; it does not interpolate.<\/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>Crown Rump Length (CRL) \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> enter 10 for Number of weeks and select mm for Unit.<\/p>\n<p>At 10 weeks, the lookup table gives \\(c_8=3.1\\) cm.<\/p>\n<p>\\[i=\\left\\lfloor 2(10-6)\\right\\rfloor=8,\\qquad \\mathrm{CRL}_{\\mathrm{mm}}=10(3.1)=31\\ \\mathrm{mm}\\]<\/p>\n<p><strong>Result:<\/strong> the estimated Crown Rump Length is 31 mm. Selecting cm instead gives 3.1 cm.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to use the calculator<\/h2>\n<ol>\n<li>Enter the gestational age in <strong>Number of weeks<\/strong>. The accepted range is 6 through 14 weeks. You can enter a decimal, such as 10.5 for 10 weeks and 3\u00bd days.<\/li>\n<li>Choose <strong>Unit<\/strong>: mm for millimeters or cm for centimeters.<\/li>\n<li>Read the estimated <strong>Crown Rump Length<\/strong>. The result is a table-based estimate, not a measurement of an individual pregnancy.<\/li>\n<\/ol>\n<p>If you need to work out how far along a pregnancy is before entering a value, use the <a href=\"https:\/\/wpcalc.com\/en\/pregnancy-baby\/gestational-age\/\">Gestational Age Calculator<\/a> or <a href=\"https:\/\/wpcalc.com\/en\/pregnancy-baby\/how-many-weeks-pregnant\/\">How Many Weeks Pregnant Are You?<\/a>. This calculator only works from weeks to length: it does not accept a measured CRL to calculate gestational age.<\/p>\n<h2>What crown\u2013rump length means<\/h2>\n<p>Crown\u2013rump length (CRL) is the distance from the top of an embryo\u2019s or fetus\u2019s head to the bottom of its buttocks. It excludes the legs. A clinician measures CRL on an ultrasound image, particularly in early pregnancy, when it can help establish gestational age and an estimated due date.<\/p>\n<p>This calculator answers a narrower question: what length does its reference table associate with a gestational age you already know? Gestational age is generally counted from the first day of the last menstrual period, not from the date of conception. The result can provide a rough point of comparison, but it cannot tell you whether a particular ultrasound measurement is expected for your pregnancy.<\/p>\n<p>An ultrasound report may use its own dating method and measurement standards. If a scan-based age differs from an age calculated from menstrual dates, ask your healthcare professional which date to use. For other ways to explore pregnancy timing, see the <a href=\"https:\/\/wpcalc.com\/en\/pregnancy-baby\/ultrasound-gestation-period\/\">Ultrasound Gestation Period<\/a> and <a href=\"https:\/\/wpcalc.com\/en\/pregnancy-baby\/pregnancy-due-date\/\">Pregnancy Due Date<\/a> calculators.<\/p>\n<h2>Reference values used by this calculator<\/h2>\n<p>These are the calculator\u2019s fixed values. The millimeter column is the centimeter value multiplied by 10; it is not a separate set of ultrasound measurements.<\/p>\n<table>\n<thead>\n<tr>\n<th>Gestational age (weeks)<\/th>\n<th>CRL (cm)<\/th>\n<th>CRL (mm)<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>6<\/td>\n<td>0.45<\/td>\n<td>4.5<\/td>\n<\/tr>\n<tr>\n<td>6.5<\/td>\n<td>0.65<\/td>\n<td>6.5<\/td>\n<\/tr>\n<tr>\n<td>7<\/td>\n<td>0.92<\/td>\n<td>9.2<\/td>\n<\/tr>\n<tr>\n<td>7.5<\/td>\n<td>1.3<\/td>\n<td>13<\/td>\n<\/tr>\n<tr>\n<td>8<\/td>\n<td>1.5<\/td>\n<td>15<\/td>\n<\/tr>\n<tr>\n<td>8.5<\/td>\n<td>1.9<\/td>\n<td>19<\/td>\n<\/tr>\n<tr>\n<td>9<\/td>\n<td>2.2<\/td>\n<td>22<\/td>\n<\/tr>\n<tr>\n<td>9.5<\/td>\n<td>2.7<\/td>\n<td>27<\/td>\n<\/tr>\n<tr>\n<td>10<\/td>\n<td>3.1<\/td>\n<td>31<\/td>\n<\/tr>\n<tr>\n<td>10.5<\/td>\n<td>3.6<\/td>\n<td>36<\/td>\n<\/tr>\n<tr>\n<td>11<\/td>\n<td>4.1<\/td>\n<td>41<\/td>\n<\/tr>\n<tr>\n<td>11.5<\/td>\n<td>4.7<\/td>\n<td>47<\/td>\n<\/tr>\n<tr>\n<td>12<\/td>\n<td>5.2<\/td>\n<td>52<\/td>\n<\/tr>\n<tr>\n<td>12.5<\/td>\n<td>6.0<\/td>\n<td>60<\/td>\n<\/tr>\n<tr>\n<td>13<\/td>\n<td>6.5<\/td>\n<td>65<\/td>\n<\/tr>\n<tr>\n<td>13.5<\/td>\n<td>7.4<\/td>\n<td>74<\/td>\n<\/tr>\n<tr>\n<td>14<\/td>\n<td>7.9<\/td>\n<td>79<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Assumptions and limitations<\/h2>\n<p>The table changes only at half-week intervals. For example, entering 10.9 weeks returns the 10.5-week value of 3.6 cm, or 36 mm; it does not estimate a value between 10.5 and 11 weeks. Entering less than 6 or more than 14 weeks produces an error rather than an extrapolated length.<\/p>\n<p>Actual CRL measurements vary, and ultrasound results depend on factors such as fetal position and how the measurement is taken. A difference between this estimate and a scan result is not, by itself, evidence of a problem. Use the ultrasound report and your clinician\u2019s interpretation for decisions about pregnancy dating or fetal development.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Estimate crown\u2013rump length from a gestational age of 6 to 14 weeks. Enter the number of weeks and choose millimeters or centimeters.<\/p>\n","protected":false},"author":70,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[45],"tags":[47],"class_list":["post-57711","post","type-post","status-publish","format-standard","hentry","category-pregnancy-baby","tag-pregnancy-tracking"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/57711","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\/70"}],"replies":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/comments?post=57711"}],"version-history":[{"count":4,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/57711\/revisions"}],"predecessor-version":[{"id":65379,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/57711\/revisions\/65379"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=57711"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=57711"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=57711"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}