{"id":826,"date":"2026-10-26T17:36:09","date_gmt":"2026-10-26T17:36:09","guid":{"rendered":"https:\/\/avexai.io\/blog\/?page_id=826"},"modified":"2026-10-26T20:17:16","modified_gmt":"2026-10-26T20:17:16","slug":"portfolio-diversification-calculator","status":"publish","type":"page","link":"https:\/\/avexai.io\/blog\/portfolio-diversification-calculator\/","title":{"rendered":"Portfolio Diversification Calculator: How Concentrated Are You Really?"},"content":{"rendered":"\n<div class=\"wp-block-group avex-bc is-layout-constrained wp-block-group-is-layout-constrained\"><span><span><a href=\"https:\/\/avexai.io\/\">Home<\/a><\/span> \u2192 <span class=\"breadcrumb_last\" aria-current=\"page\">Blog<\/span><\/span>\n<\/div>\n\n\n\n<style>body.page-id-826 main{max-width:800px;margin-left:auto;margin-right:auto;padding:0 24px;box-sizing:border-box}<\/style>\n\n\n\n<style>body.page-id-826 main{max-width:800px;margin-left:auto;margin-right:auto;padding:0 24px;box-sizing:border-box}<\/style>\n\n\n\n<style>body.page-id-NNN main{max-width:800px;margin-left:auto;margin-right:auto;padding:0 24px;box-sizing:border-box}<\/style>\n\n<div class=\"avex-quick-answer\">\n  <div class=\"qa-label\">Quick answer<\/div>\n  <p><strong>Diversification is a question of weights, not line count \u2014 and this calculator measures the weights.<\/strong> It converts holdings and weights into an &#8220;effective number of holdings&#8221; (the number of equal-sized positions the portfolio behaves like), flags any single position above the common 10% guideline, and shows how much of the total sits in the top three names. Nothing leaves the browser.<\/p><\/div>\n\n\n<div class=\"avex-w-cc\">\r\n  <style>\r\n    .avex-w-cc { --o:#ea580c; --o2:#f97316; --od:#c2410c; --n:#0a2540; --pb:#fed7aa; --pl:#fffbf7; --pbg:#fff4e6; font-family:'Inter',-apple-system,BlinkMacSystemFont,sans-serif; line-height:1.6; margin:28px 0; }\r\n    .avex-w-cc * { box-sizing:border-box; margin:0; padding:0; }\r\n    .avex-w-cc .c { background:#fff; border:1px solid var(--pb); border-radius:20px; box-shadow:0 20px 50px rgba(234,88,12,.10); overflow:hidden; max-width:880px; margin:0 auto; }\r\n    .avex-w-cc .g { display:grid; grid-template-columns:1fr 1.1fr; }\r\n    .avex-w-cc .in { padding:34px; border-right:1px solid #f5e6d3; }\r\n    .avex-w-cc .in h2 { font-size:19px; font-weight:700; color:var(--n); margin-bottom:4px; }\r\n    .avex-w-cc .hint { font-size:13.5px; color:#555; margin-bottom:16px; }\r\n    .avex-w-cc textarea { width:100%; min-height:220px; font-family:'SF Mono',Menlo,monospace; font-size:13.5px; padding:14px; border:1.5px solid var(--pb); border-radius:10px; background:var(--pl); color:var(--n); resize:vertical; line-height:1.7; }\r\n    .avex-w-cc textarea:focus { outline:none; border-color:var(--o); background:#fff; }\r\n    .avex-w-cc .demo { margin-top:12px; font-family:inherit; font-size:13.5px; font-weight:600; padding:10px 16px; border:1.5px solid var(--pb); border-radius:9px; background:#fff; color:var(--n); cursor:pointer; }\r\n    .avex-w-cc .demo:hover { border-color:var(--o); color:var(--o); }\r\n    .avex-w-cc .res { padding:34px; background:var(--n); color:#fff; display:flex; flex-direction:column; justify-content:center; }\r\n    .avex-w-cc .rl { font-size:12px; font-weight:600; text-transform:uppercase; letter-spacing:.09em; color:#94a3b8; margin-bottom:8px; }\r\n    .avex-w-cc .big { font-size:46px; font-weight:800; letter-spacing:-.03em; line-height:1.05; color:#fff; }\r\n    .avex-w-cc .sub { font-size:14px; color:#cbd5e1; margin-top:10px; }\r\n    .avex-w-cc .brk { margin-top:20px; padding-top:16px; border-top:1px solid rgba(255,255,255,.12); }\r\n    .avex-w-cc .r { display:flex; justify-content:space-between; font-size:13.5px; margin-bottom:8px; gap:12px; }\r\n    .avex-w-cc .r .k { color:#94a3b8; }\r\n    .avex-w-cc .r .v { color:#fff; font-weight:600; text-align:right; }\r\n    .avex-w-cc .flag { display:inline-block; padding:4px 11px; border-radius:14px; font-size:12px; font-weight:700; }\r\n    .avex-w-cc .warn-list { margin-top:14px; }\r\n    .avex-w-cc .warn-list div { font-size:13px; color:#fecaca; margin-bottom:6px; }\r\n    .avex-w-cc .warn-list div.ok { color:#bbf7d0; }\r\n    .avex-w-cc .cta { padding:22px 34px; background:var(--pbg); border-top:1px solid var(--pb); display:flex; align-items:center; justify-content:space-between; gap:18px; flex-wrap:wrap; }\r\n    .avex-w-cc .cta .t { font-size:14.5px; color:var(--n); font-weight:600; }\r\n    .avex-w-cc .cta .t span { display:block; font-weight:400; color:#555; font-size:13px; }\r\n    .avex-w-cc .btn { display:inline-block; background:var(--o); color:#fff !important; font-weight:600; font-size:14.5px; padding:11px 22px; border-radius:8px; text-decoration:none; box-shadow:0 4px 14px rgba(234,88,12,.25); }\r\n    .avex-w-cc .btn:hover { background:var(--od); }\r\n    .avex-w-cc .note { text-align:center; font-size:12px; color:#888; font-style:italic; max-width:700px; margin:12px auto 0; }\r\n    @media (max-width:820px){ .avex-w-cc .g { grid-template-columns:1fr; } .avex-w-cc .in { border-right:none; border-bottom:1px solid #f5e6d3; } }\r\n  <\/style>\r\n  <div class=\"c\">\r\n    <div class=\"g\">\r\n      <div class=\"in\">\r\n        <h2>Your holdings &amp; weights<\/h2>\r\n        <div class=\"hint\">One per line: <code>TICKER weight%<\/code> \u2014 weights are normalised automatically. Nothing leaves your browser.<\/div>\r\n        <textarea id=\"cc-input\" spellcheck=\"false\">NVDA 22\r\nVOO 30\r\nAAPL 12\r\nMSFT 10\r\nTSLA 8\r\nBND 10\r\nOther 8<\/textarea>\r\n        <button type=\"button\" class=\"demo\" id=\"cc-demo\">Load a diversified example<\/button>\r\n      <\/div>\r\n      <div class=\"res\">\r\n        <div class=\"rl\">Effective number of holdings<\/div>\r\n        <div class=\"big\" id=\"cc-eff\">\u2014<\/div>\r\n        <div class=\"sub\" id=\"cc-sub\">\u2026<\/div>\r\n        <div class=\"brk\">\r\n          <div class=\"r\"><span class=\"k\">Largest position<\/span><span class=\"v\" id=\"cc-top1\">\u2014<\/span><\/div>\r\n          <div class=\"r\"><span class=\"k\">Top 3 combined<\/span><span class=\"v\" id=\"cc-top3\">\u2014<\/span><\/div>\r\n          <div class=\"r\"><span class=\"k\">HHI (0\u201310,000)<\/span><span class=\"v\" id=\"cc-hhi\">\u2014<\/span><\/div>\r\n          <div class=\"r\"><span class=\"k\">Verdict<\/span><span class=\"v\"><span class=\"flag\" id=\"cc-flag\">\u2014<\/span><\/span><\/div>\r\n        <\/div>\r\n        <div class=\"warn-list\" id=\"cc-warns\"><\/div>\r\n      <\/div>\r\n    <\/div>\r\n    <div class=\"cta\">\r\n      <div class=\"t\">This checks tickers. Avex checks what's <em>inside<\/em> them.\r\n        <span>ETF look-through: your \"diversified\" funds may hold the same stocks twice.<\/span>\r\n      <\/div>\r\n      <a class=\"btn\" href=\"https:\/\/app.avexai.io\/register\">Create an account \u2192<\/a>\r\n    <\/div>\r\n  <\/div>\r\n  <p class=\"note\">Heuristics: effective holdings = 1 \u00f7 \u03a3(weight\u00b2) \u2014 how many equal-sized positions your concentration is equivalent to. The 10% single-position line is a common risk-management convention, not a rule. Treats each line as independent \u2014 ETFs count as one holding here (their look-through requires holdings data). Mathematical context only \u2014 not investment advice.<\/p>\r\n  <script>\r\n  (function(){\r\n    var $=function(id){return document.getElementById(id)};\r\n    function parse(text){\r\n      var rows=[];\r\n      text.split(\/\\r?\\n\/).forEach(function(line){\r\n        var m=line.trim().match(\/^(.+?)[\\s,;:]+(-?\\d+(?:[.,]\\d+)?)\\s*%?$\/);\r\n        if(!m) return;\r\n        var w=parseFloat(m[2].replace(',','.'));\r\n        if(w>0) rows.push({name:m[1].trim().toUpperCase(), w:w});\r\n      });\r\n      return rows;\r\n    }\r\n    function calc(){\r\n      var rows=parse($('cc-input').value);\r\n      var warns=$('cc-warns'); warns.innerHTML='';\r\n      if(rows.length<2){ $('cc-eff').textContent='\u2014'; $('cc-sub').textContent='Add at least two holdings.'; ['cc-top1','cc-top3','cc-hhi'].forEach(function(i){$(i).textContent='\u2014'}); $('cc-flag').textContent='\u2014'; return; }\r\n      var sum=rows.reduce(function(a,r){return a+r.w},0);\r\n      var ws=rows.map(function(r){return {name:r.name, w:r.w\/sum}});\r\n      ws.sort(function(a,b){return b.w-a.w});\r\n      var hhi=ws.reduce(function(a,r){return a+r.w*r.w},0);\r\n      var eff=1\/hhi;\r\n      var top1=ws[0], top3=ws.slice(0,3).reduce(function(a,r){return a+r.w},0);\r\n      $('cc-eff').textContent=eff.toFixed(1);\r\n      $('cc-sub').textContent='Your '+rows.length+' holdings behave like '+eff.toFixed(1)+' equal-sized positions.';\r\n      $('cc-top1').textContent=top1.name+' \u2014 '+(top1.w*100).toFixed(1)+'%';\r\n      $('cc-top3').textContent=(top3*100).toFixed(1)+'%';\r\n      $('cc-hhi').textContent=Math.round(hhi*10000).toLocaleString('en-GB');\r\n      var f=$('cc-flag'), v;\r\n      if(hhi<0.10) v={t:'Diversified',bg:'#dcfce7',fg:'#16a34a'};\r\n      else if(hhi<0.18) v={t:'Moderately concentrated',bg:'#fef3c7',fg:'#b45309'};\r\n      else v={t:'Concentrated',bg:'#fee2e2',fg:'#dc2626'};\r\n      f.textContent=v.t; f.style.background=v.bg; f.style.color=v.fg;\r\n      if(Math.abs(sum-100)>1) warns.innerHTML+='<div>\u2139\ufe0f Weights summed to '+sum.toFixed(1)+' \u2014 normalised to 100%.<\/div>';\r\n      ws.filter(function(r){return r.w>0.10}).forEach(function(r){\r\n        warns.innerHTML+='<div>\u26a0\ufe0f '+r.name+' is '+(r.w*100).toFixed(1)+'% \u2014 above the common 10% single-position guideline.<\/div>';\r\n      });\r\n      if(!ws.some(function(r){return r.w>0.10})) warns.innerHTML+='<div class=\"ok\">\u2713 No single position above the 10% guideline.<\/div>';\r\n    }\r\n    $('cc-input').addEventListener('input',calc);\r\n    $('cc-demo').addEventListener('click',function(){\r\n      $('cc-input').value='VTI 40\\nBND 20\\nVXUS 15\\nQQQ 8\\nSCHD 7\\nVNQ 5\\nCash 5';\r\n      calc();\r\n    });\r\n    calc();\r\n  })();\r\n  <\/script>\r\n<\/div>\n\n\n\n<p style=\"text-align:center;font-size:13px;color:#555\"><span style=\"display:inline-block;width:8px;height:8px;border-radius:50%;background:#4ade80;margin-right:6px\"><\/span>Runs 100% in your browser. Nothing is uploaded, ever.<\/p>\n\n<h2>How is diversification calculated here?<\/h2>\n<p><strong>With the Herfindahl\u2013Hirschman Index (HHI) \u2014 the concentration measure antitrust regulators apply to markets \u2014 applied to portfolio weights.<\/strong> Square each holding&#8217;s weight and add the squares: the result sits between 0 (infinitely spread) and 1 (everything in one position). Its reciprocal is the effective number of holdings, and it is the more honest figure: twenty positions where one is 60% of the portfolio behave like fewer than three equal-sized ones.<sup style=\"font-size:11px;color:#c2410c\">[1]<\/sup><\/p>\n<div class=\"avex-pro-tip\" style=\"font-family:Menlo,monospace;font-size:14px\">HHI = \u03a3 (weight\u1d62)\u00b2   \u00b7   Effective holdings = 1 \u00f7 HHI<\/div>\n<p>The verdict bands on this page \u2014 diversified below 0.10, moderately concentrated to 0.18, concentrated above \u2014 are analytical conventions chosen for readability, not regulatory thresholds. The 10% single-position flag follows a widely used risk-management guideline, not a rule.<sup style=\"font-size:11px;color:#c2410c\">[2][3]<\/sup><\/p>\n\n<h2>What counts as a concentrated portfolio?<\/h2>\n<p><strong>There is no official number \u2014 but investor-education sources and advisers cite the same ranges with minor variation.<\/strong> They are starting points for a decision, not instructions.<\/p>\n<table class=\"avex-comparison-table\"><tr><th>Single position<\/th><th>How it is commonly read<\/th><th>Source of the convention<\/th><\/tr>\n<tr><td>Under 5%<\/td><td>Conservative, well diversified<\/td><td>T. Rowe Price flags holdings above 5% as worth addressing, especially company stock<sup style=\"font-size:11px;color:#c2410c\">[2]<\/sup><\/td><\/tr>\n<tr><td>5\u201310%<\/td><td>Acceptable for a high-conviction position, monitored<\/td><td>Common adviser guideline; Fidelity&#8217;s education pages discuss why a large single holding deserves review<sup style=\"font-size:11px;color:#c2410c\">[3]<\/sup><\/td><\/tr>\n<tr><td>10\u201320%<\/td><td>Meaningful concentration; one company can dominate results<\/td><td>The 10% line is the most-cited convention; this calculator flags it<\/td><\/tr>\n<tr><td>Over 20%<\/td><td>Single-company risk drives the portfolio<\/td><td>Widely described as over-concentration<\/td><\/tr><\/table>\n\n<h2>What this tool doesn&#8217;t do<\/h2>\n<p><strong>It treats every line as independent \u2014 which is exactly what a portfolio is not.<\/strong> An S&amp;P 500 fund counts as one holding here, although its ten largest companies make up a large share of the index and are very likely in the growth fund and the individual shares next to it. Seeing through funds to the companies inside them \u2014 look-through \u2014 requires holdings data this page does not have. That is a tracker&#8217;s job; Avex does it from exported statements. The calculator also ignores correlation, currency and sector: two different banks are two lines here, and one bet in reality.<\/p>\n<p>The question behind these numbers \u2014 how much in one stock is too much \u2014 has its own guide: <a href=\"https:\/\/avexai.io\/blog\/how-much-of-portfolio-in-one-stock\/\">what the common thresholds say<\/a>. What a concentrated position does when markets fall is the <a href=\"https:\/\/avexai.io\/blog\/drawdown-simulator\/\">drawdown simulator<\/a>&#8216;s job.<\/p>\n\n\n\n<div class=\"schema-faq wp-block-yoast-faq-block\"><div class=\"schema-faq-section\" id=\"faq-question-1793034910047\"><strong class=\"schema-faq-question\">What is a good effective number of holdings?<\/strong> <p class=\"schema-faq-answer\">Higher is more diversified \u2014 but there is no target. A portfolio of broad index funds scores far above its line count because weights are spread thinly inside each fund; a portfolio with one dominant stock scores low, however many lines it has. The figure is for comparing before and after a change, not for benchmarking.<br><\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1793034938034\"><strong class=\"schema-faq-question\">Does this calculator see inside ETFs and mutual funds?<\/strong> <p class=\"schema-faq-answer\">No \u2014 each fund is one holding here. Overlap between funds, and between funds and the individual shares held alongside them, is exactly what this page cannot measure. A tracker with holdings data can; this calculator is the quick check before that.<br><\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1793034977065\"><strong class=\"schema-faq-question\">How much of my portfolio should be in one stock?<\/strong> <p class=\"schema-faq-answer\">Investor-education sources most often cite 5% as conservative and 10% as the line where a single company starts to dominate results; above 20% is widely described as over-concentration. These are conventions, not rules, and the right figure depends on the rest of your wealth and on whether the stock is also your employer.<br><\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1793034998231\"><strong class=\"schema-faq-question\">Should I count my employer stock and my 401(k) here?<\/strong> <p class=\"schema-faq-answer\">For a true picture, yes: concentration is measured against total wealth, not one account. Vested employer shares, an ESPP and the company-stock fund inside a 401(k) are the same bet as the shares you hold in a brokerage account.<br><\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1793035021267\"><strong class=\"schema-faq-question\">Is my data uploaded?<\/strong> <p class=\"schema-faq-answer\">No \u2014 the calculation runs entirely in the browser, and nothing pasted here leaves the page. Avex itself works from statement files the user chooses to upload, not from broker logins.<br><\/p> <\/div> <\/div>\n\n\n\n<div class=\"avex-sources\">\n  <h3>Sources &amp; references<\/h3><ol>\n<li><a href=\"https:\/\/www.justice.gov\/atr\/herfindahl-hirschman-index\">U.S. Department of Justice: Herfindahl\u2013Hirschman Index (definition)<\/a><\/li>\n<li><a href=\"https:\/\/www.troweprice.com\/personal-investing\/resources\/insights\/actions-can-take-if-your-portfolio-is-too-concentrated-in-one-equity.html\">T. Rowe Price: Actions you can take if your portfolio is too concentrated in one equity<\/a><\/li>\n<li><a href=\"https:\/\/www.fidelity.com\/learning-center\/trading-investing\/too-much-one-investment\">Fidelity Learning Center: Do you hold too much in one investment?<\/a><\/li>\n<\/ol>\n  <p style=\"font-size:13px;color:#777;margin-top:12px\">Last verified: 22 October 2026.<\/p>\n<\/div>\n\n\n\n<div style=\"background:radial-gradient(ellipse 70% 80% at 0% 0%,rgba(227,114,4,.8) 0%,rgba(227,114,4,.25) 40%,transparent 65%),radial-gradient(ellipse 60% 70% at 100% 100%,rgba(246,167,0,.5) 0%,transparent 60%),linear-gradient(180deg,#000814 0%,#001D3D 100%);color:#fff!important;padding:56px 32px!important;text-align:center!important;margin:48px 0;border-radius:16px;border:1px solid rgba(255,165,50,.18)\">\n  <div style=\"display:inline-block;font-size:11px!important;text-transform:uppercase!important;letter-spacing:1.5px!important;color:#001D3D!important;background:#FFCC33!important;padding:5px 12px!important;border-radius:4px!important;font-weight:700!important;margin:0 0 16px!important;line-height:1.4!important\">Private Wealth Copilot<\/div>\n  <div style=\"font-size:30px!important;margin:0 0 14px!important;letter-spacing:-.5px!important;color:#ffffff!important;font-weight:700!important;line-height:1.2!important\">This checks tickers. Avex checks what&#8217;s inside them.<\/div>\n  <div style=\"color:rgba(255,255,255,.75)!important;margin:0 auto 28px!important;font-size:17px!important;max-width:560px!important;line-height:1.6!important;font-weight:400!important\">Paste a list here and you get weights. Upload your statements to Avex and you get the look-through: the same companies held through \n    three funds, across every broker you use. Read-only by design.<\/div>\n  <a href=\"https:\/\/avexai.io\/contact\" style=\"background:#E37204!important;color:#ffffff!important;padding:14px 32px!important;border-radius:8px!important;font-weight:600!important;text-decoration:none!important;display:inline-block!important;font-size:15px!important;margin:4px 6px!important;text-transform:none!important;letter-spacing:0!important;border:none!important;box-shadow:none!important\">Request Early Access<\/a>\n  <a href=\"https:\/\/avexai.io\/#platform\" style=\"background:transparent!important;color:#ffffff!important;padding:14px 32px!important;border-radius:8px!important;font-weight:600!important;text-decoration:none!important;display:inline-block!important;font-size:15px!important;margin:4px 6px!important;text-transform:none!important;letter-spacing:0!important;border:1.5px solid rgba(255,255,255,.3)!important;box-shadow:none!important\">See the Platform<\/a>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Quick answer Diversification is a question of weights, not line count \u2014 and this calculator measures the weights. It converts holdings and weights into an &#8220;effective number of holdings&#8221; (the number of equal-sized positions the portfolio behaves like), flags any single position above the common 10% guideline, and shows how much of the total sits [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":845,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_angie_page":false,"footnotes":"","_wp_rev_ctl_limit":""},"class_list":["post-826","page","type-page","status-publish","has-post-thumbnail","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.8 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Portfolio Diversification Calculator: How Concentrated Are You?<\/title>\n<meta name=\"description\" content=\"Free portfolio diversification calculator: paste your holdings and weights to get your effective number of holdings, largest position and a concentration verdict. 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