{"id":100250,"date":"2026-02-15T20:29:43","date_gmt":"2026-02-15T20:29:43","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100250"},"modified":"2026-03-05T15:40:17","modified_gmt":"2026-03-05T15:40:17","slug":"surface-parameters-iso21920","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/nb\/calculators\/surface-parameters-iso21920\/","title":{"rendered":"Overflateruhetskalkulator Ra Rz Rq Rt | ISO 21920"},"content":{"rendered":"\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"Surface Parameters Calculator ISO 21920\",\"description\":\"Free ISO 21920 surface profile parameters. Estimate Rz, Rq, Rt from Ra. Filter cutoff reference.\",\"url\":\"https:\/\/vibromera.eu\/calculators\/surface-parameters-iso21920\/\",\"applicationCategory\":\"Engineering Calculator\",\"operatingSystem\":\"Any (Web Browser)\",\"offers\":{\"@type\":\"Offer\",\"price\":\"0\",\"priceCurrency\":\"EUR\"},\"creator\":{\"@type\":\"Organization\",\"name\":\"Vibromera\",\"url\":\"https:\/\/vibromera.eu\/\"},\"datePublished\":\"2024-01-01\",\"dateModified\":\"2025-06-01\",\"inLanguage\":\"en\",\"isAccessibleForFree\":true}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"mainEntity\":[\n{\"@type\":\"Question\",\"name\":\"What is the difference between Ra and Rz?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Ra is the arithmetical mean roughness (average deviation from mean line). Rz is the maximum height of the profile (average of 5 highest peaks to 5 deepest valleys). Rz is typically 4-7 times Ra for machined surfaces.\"}},\n{\"@type\":\"Question\",\"name\":\"What filter cutoff should I use?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"ISO 21920 specifies default cutoff wavelengths: \u03bbc = 0.08 mm for Ra \u2264 0.1 \u03bcm, \u03bbc = 0.25 mm for Ra 0.1-2 \u03bcm, \u03bbc = 0.8 mm for Ra 2-10 \u03bcm, \u03bbc = 2.5 mm for Ra 10-80 \u03bcm, \u03bbc = 8 mm for Ra > 80 \u03bcm.\"}},\n{\"@type\":\"Question\",\"name\":\"What is Rq?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Rq (root mean square roughness) is the RMS of the profile deviations. Rq \u2248 1.11 \u00d7 Ra for a random (Gaussian) profile. Rq is more sensitive to peaks and valleys than Ra.\"}},\n{\"@type\":\"Question\",\"name\":\"What is Rt?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Rt (total height of profile) is the vertical distance between the highest peak and the deepest valley across the entire evaluation length. Rt \u2265 Rz always. Rt is highly sensitive to scratches and defects.\"}},\n{\"@type\":\"Question\",\"name\":\"How does ISO 21920 differ from the old ISO 4287?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"ISO 21920 replaces the older ISO 4287 and ISO 3274 standards. It consolidates profile parameter definitions, measurement procedures, and filter specifications into a single updated standard series.\"}}\n]}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"BreadcrumbList\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/vibromera.eu\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Calculators\",\"item\":\"https:\/\/vibromera.eu\/calculators\/\"},{\"@type\":\"ListItem\",\"position\":3,\"name\":\"Surface Parameters ISO 21920\",\"item\":\"https:\/\/vibromera.eu\/calculators\/surface-parameters-iso21920\/\"}]}\n<\/script>\n\n<link rel=\"preconnect\" href=\"https:\/\/fonts.googleapis.com\">\n\n<link rel=\"preconnect\" href=\"https:\/\/fonts.gstatic.com\" crossorigin>\n\n<link href=\"https:\/\/fonts.googleapis.com\/css2?family=DM+Sans:ital,opsz,wght@0,9..40,300;0,9..40,400;0,9..40,500;0,9..40,600;0,9..40,700;1,9..40,400&#038;family=JetBrains+Mono:wght@400;500;600&#038;family=Fraunces:opsz,wght@9..144,700;9..144,800&#038;display=swap\" rel=\"stylesheet\">\n\n<link rel=\"stylesheet\" href=\"https:\/\/cdn.jsdelivr.net\/npm\/katex@0.16.11\/dist\/katex.min.css\">\n\n<style>\n:root{--vc-bg:#f4f1ec;--vc-surface:#fff;--vc-surface-alt:#f8f6f2;--vc-ink:#1a1a1a;--vc-ink-secondary:#5a5650;--vc-ink-muted:#8a857e;--vc-accent:#c85a2a;--vc-accent-hover:#b04d22;--vc-accent-light:#fdf0ea;--vc-blue:#2a5c8c;--vc-blue-light:#eaf1f8;--vc-green:#2a7a4b;--vc-green-light:#eaf8ef;--vc-yellow:#a67c00;--vc-yellow-light:#fef9e8;--vc-red:#b91c1c;--vc-red-light:#fef2f2;--vc-border:#d9d4cc;--vc-border-light:#e8e4dd;--vc-shadow:0 1px 3px rgba(26,26,26,.06),0 4px 12px rgba(26,26,26,.04);--vc-radius:8px;--vc-radius-lg:12px;--vc-font:'DM Sans',-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif;--vc-mono:'JetBrains Mono',Consolas,Monaco,monospace;--vc-display:'Fraunces',Georgia,serif}.vc-calculator{font-family:var(--vc-font);font-size:15px;line-height:1.65;color:var(--vc-ink);max-width:960px;margin:0 auto;padding:20px 16px 40px;-webkit-font-smoothing:antialiased}.vc-calculator *,.vc-calculator *::before,.vc-calculator *::after{box-sizing:border-box}.vc-header{text-align:center;padding:48px 24px 40px;position:relative}.vc-header::after{content:'';position:absolute;bottom:0;left:50%;transform:translateX(-50%);width:80px;height:3px;background:var(--vc-accent);border-radius:2px}.vc-header-eyebrow{font-family:var(--vc-mono);font-size:11px;font-weight:500;letter-spacing:.15em;text-transform:uppercase;color:var(--vc-accent);margin:0 0 12px}.vc-header-title{font-family:var(--vc-display);font-size:clamp(24px,4vw,36px);font-weight:800;line-height:1.15;color:var(--vc-ink);margin:0 0 16px;letter-spacing:-.02em}.vc-header-subtitle{font-size:15px;color:var(--vc-ink-secondary);margin:0 auto 20px;max-width:600px}.vc-badges{display:inline-flex;gap:8px;flex-wrap:wrap;justify-content:center}.vc-badge{font-family:var(--vc-mono);font-size:11px;font-weight:500;padding:4px 10px;border-radius:4px;background:var(--vc-surface);border:1px solid var(--vc-border);color:var(--vc-ink-secondary)}.vc-card{background:var(--vc-surface);border:1px solid var(--vc-border);border-radius:var(--vc-radius-lg);box-shadow:var(--vc-shadow);overflow:hidden;margin-top:32px}.vc-form{padding:24px}.vc-form-grid{display:grid;grid-template-columns:1fr 1fr;gap:18px}@media(max-width:600px){.vc-form-grid{grid-template-columns:1fr}}.vc-field{display:flex;flex-direction:column}.vc-label{font-size:12px;font-weight:600;letter-spacing:.04em;text-transform:uppercase;color:var(--vc-ink-secondary);margin-bottom:6px}.vc-label-hint{font-weight:400;text-transform:none;letter-spacing:0;color:var(--vc-ink-muted);font-size:11px}.vc-select,.vc-input{width:100%;padding:10px 12px;border:1.5px solid var(--vc-border);border-radius:6px;font-family:var(--vc-font);font-size:14px;color:var(--vc-ink);background:var(--vc-surface);transition:border-color .15s,box-shadow .15s}.vc-select{padding-right:36px;appearance:none;-webkit-appearance:none;cursor:pointer;background-image:url(\"data:image\/svg+xml,%3Csvg xmlns='http:\/\/www.w3.org\/2000\/svg' width='16' height='16' fill='none' stroke='%235a5650' stroke-width='2'%3E%3Cpath d='M4 6l4 4 4-4'\/%3E%3C\/svg%3E\");background-repeat:no-repeat;background-position:right 10px center}.vc-select:focus,.vc-input:focus{outline:none;border-color:var(--vc-accent);box-shadow:0 0 0 3px rgba(200,90,42,.12)}.vc-presets{display:flex;flex-wrap:wrap;gap:8px;margin-top:18px;padding-top:18px;border-top:1px solid var(--vc-border-light)}.vc-presets-label{font-family:var(--vc-mono);font-size:11px;font-weight:500;letter-spacing:.1em;text-transform:uppercase;color:var(--vc-ink-muted);width:100%;margin-bottom:2px}.vc-preset-btn{padding:5px 12px;font-family:var(--vc-font);font-size:12px;font-weight:500;border:1px solid var(--vc-border);border-radius:6px;background:var(--vc-surface-alt);color:var(--vc-ink-secondary);cursor:pointer;transition:all .15s}.vc-preset-btn:hover{border-color:var(--vc-accent);color:var(--vc-accent);background:var(--vc-accent-light)}.vc-results{border-top:1px solid var(--vc-border-light);background:var(--vc-surface-alt);padding:0;max-height:0;overflow:hidden;transition:max-height .5s cubic-bezier(.4,0,.2,1),padding .3s}.vc-results.vc-visible{max-height:2000px;padding:24px}.vc-results-head{display:flex;align-items:center;justify-content:space-between;margin-bottom:18px}.vc-results-title{font-family:var(--vc-display);font-size:20px;font-weight:700;color:var(--vc-ink);margin:0}.vc-copy-btn{display:inline-flex;align-items:center;gap:5px;padding:6px 12px;border:1px solid var(--vc-border);border-radius:6px;background:var(--vc-surface);font-family:var(--vc-font);font-size:12px;font-weight:500;color:var(--vc-ink-secondary);cursor:pointer;transition:all .15s}.vc-copy-btn:hover{border-color:var(--vc-accent);color:var(--vc-accent)}.vc-copy-btn.vc-copied{background:var(--vc-green-light);border-color:var(--vc-green);color:var(--vc-green)}.vc-result-grid{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin-bottom:20px}@media(max-width:500px){.vc-result-grid{grid-template-columns:1fr}}.vc-rcard{background:var(--vc-surface);border:1px solid var(--vc-border-light);border-radius:var(--vc-radius);padding:16px;transition:transform .2s}.vc-rcard:hover{transform:translateY(-1px)}.vc-rcard-primary{border-color:var(--vc-accent);border-width:2px;background:linear-gradient(135deg,#fdf6f2,var(--vc-surface));grid-column:1\/-1}.vc-rcard-label{font-family:var(--vc-mono);font-size:10px;font-weight:500;letter-spacing:.1em;text-transform:uppercase;color:var(--vc-ink-muted);margin-bottom:4px}.vc-rcard-value{font-family:var(--vc-mono);font-size:22px;font-weight:600;color:var(--vc-ink);line-height:1.2}.vc-rcard-primary .vc-rcard-value{font-size:30px;color:var(--vc-accent)}.vc-rcard-unit{font-size:14px;font-weight:400;color:var(--vc-ink-secondary)}.vc-section{margin-top:24px;border:1px solid var(--vc-border);border-radius:var(--vc-radius-lg);background:var(--vc-surface);box-shadow:var(--vc-shadow);overflow:hidden}.vc-section-toggle{width:100%;display:flex;align-items:center;justify-content:space-between;padding:18px 24px;border:none;background:transparent;cursor:pointer;font-family:var(--vc-font);text-align:left;transition:background .15s}.vc-section-toggle:hover{background:var(--vc-surface-alt)}.vc-section-toggle-text{display:flex;align-items:center;gap:10px}.vc-section-icon{font-size:20px;line-height:1}.vc-section-title{font-family:var(--vc-display);font-size:18px;font-weight:700;color:var(--vc-ink);margin:0}.vc-section-chevron{width:20px;height:20px;color:var(--vc-ink-muted);transition:transform .3s;flex-shrink:0}.vc-section.vc-open .vc-section-chevron{transform:rotate(180deg)}.vc-section-body{max-height:0;overflow:hidden;transition:max-height .4s cubic-bezier(.4,0,.2,1)}.vc-section.vc-open .vc-section-body{max-height:20000px}.vc-section-inner{padding:0 24px 24px;border-top:1px solid var(--vc-border-light)}.vc-theory h3{font-family:var(--vc-display);font-size:17px;font-weight:700;color:var(--vc-ink);margin:28px 0 10px}.vc-theory h3:first-child{margin-top:20px}.vc-theory p{font-size:14px;color:var(--vc-ink-secondary);margin:0 0 10px}.vc-formula-box{background:var(--vc-surface-alt);border:2px solid var(--vc-border);border-radius:6px;padding:14px 20px;font-family:var(--vc-mono);font-size:16px;font-weight:500;text-align:center;margin:14px 0;color:var(--vc-ink);overflow-x:auto}.vc-table{width:100%;border-collapse:collapse;margin:14px 0;font-size:13px}.vc-table th,.vc-table td{padding:10px 12px;border:1px solid var(--vc-border-light);text-align:left}.vc-table th{background:var(--vc-surface-alt);font-size:11px;font-weight:600;text-transform:uppercase;letter-spacing:.05em;color:var(--vc-ink-secondary)}.vc-table tr:nth-child(even){background:var(--vc-surface-alt)}.vc-info-box{background:var(--vc-blue-light);border-left:3px solid var(--vc-blue);padding:14px 16px;border-radius:0 6px 6px 0;margin:14px 0}.vc-info-box p{margin:0;font-size:14px;color:var(--vc-ink-secondary)}.vc-faq-list{display:flex;flex-direction:column;gap:8px;margin-top:20px}.vc-faq-item{border:1px solid var(--vc-border-light);border-radius:6px;overflow:hidden}.vc-faq-q{width:100%;display:flex;align-items:center;justify-content:space-between;gap:12px;padding:14px 16px;border:none;background:var(--vc-surface-alt);cursor:pointer;font-family:var(--vc-font);font-size:15px;font-weight:600;color:var(--vc-ink);text-align:left;transition:background .15s}.vc-faq-q:hover{background:#ede9e3}.vc-faq-chevron{width:16px;height:16px;color:var(--vc-ink-muted);flex-shrink:0;transition:transform .25s}.vc-faq-item.vc-open .vc-faq-chevron{transform:rotate(180deg)}.vc-faq-a{max-height:0;overflow:hidden;transition:max-height .35s}.vc-faq-item.vc-open .vc-faq-a{max-height:1200px}.vc-faq-a-inner{padding:14px 16px;border-top:1px solid var(--vc-border-light);font-size:14px;color:var(--vc-ink-secondary)}.vc-faq-a-inner p{margin:0 0 8px}.vc-faq-a-inner p:last-child{margin-bottom:0}.vc-related{display:flex;flex-wrap:wrap;gap:10px;margin-top:16px}.vc-related-link{display:inline-block;padding:8px 16px;font-family:var(--vc-font);font-size:13px;font-weight:600;background:var(--vc-surface-alt);color:var(--vc-ink-secondary);border:1px solid var(--vc-border);border-radius:var(--vc-radius);text-decoration:none;transition:all .15s}.vc-related-link:hover{border-color:var(--vc-accent);color:var(--vc-accent);background:var(--vc-accent-light)}.vc-promo{margin-top:24px;padding:20px;background:linear-gradient(135deg,var(--vc-accent-light),var(--vc-surface));border:1px solid var(--vc-border);border-radius:var(--vc-radius-lg);display:flex;align-items:center;gap:16px}.vc-promo-text{flex:1;font-size:14px;color:var(--vc-ink-secondary)}.vc-promo-text strong{color:var(--vc-ink)}.vc-promo-link{padding:8px 20px;font-size:13px;font-weight:700;color:#fff;background:var(--vc-accent);border-radius:var(--vc-radius);text-decoration:none;white-space:nowrap;transition:background .15s}.vc-promo-link:hover{background:var(--vc-accent-hover)}.vc-footer{text-align:center;padding:32px 16px;font-size:13px;color:var(--vc-ink-muted)}.vc-footer a{color:var(--vc-accent);text-decoration:none}.vc-footer a:hover{text-decoration:underline}.vc-footer-links{margin-top:8px;font-size:12px}.vc-footer-links a{margin:0 8px}@media print{.vc-section-body{max-height:none!important}.vc-faq-a{max-height:none!important}.vc-results{max-height:none!important;padding:24px!important}.vc-copy-btn,.vc-section-chevron,.vc-faq-chevron,.vc-presets,.vc-promo{display:none!important}}\n<\/style>\n\n<div class=\"vc-calculator\" id=\"vc-surface-params\">\n<header class=\"vc-header\"><p class=\"vc-header-eyebrow\">Free Engineering Tool<\/p><h1 class=\"vc-header-title\">Surface Parameters Calculator \u2014 ISO 21920<\/h1><p class=\"vc-header-subtitle\">Enter Ra value or measurement data to see estimated Rz, Rq, Rt relationships and recommended filter cutoff per ISO 21920.<\/p><div class=\"vc-badges\"><span class=\"vc-badge\">ISO 21920<\/span><span class=\"vc-badge\">Ra \/ Rz \/ Rq \/ Rt<\/span><span class=\"vc-badge\">Filter Cutoff<\/span><\/div><\/header>\n\n<div class=\"vc-card\">\n    <form class=\"vc-form\" id=\"vc-form\" autocomplete=\"off\">\n        <div class=\"vc-form-grid\">\n            <div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-ra\">Ra Value <span class=\"vc-label-hint\">(\u03bcm)<\/span><\/label><input class=\"vc-input\" type=\"number\" id=\"vc-ra\" step=\"any\" min=\"0.001\" value=\"1.6\" placeholder=\"e.g. 1.6\"><\/div>\n            <div class=\"vc-field\"><label class=\"vc-label\" for=\"vc-profile\">Profile Type <span class=\"vc-label-hint\">(affects Rz\/Ra ratio)<\/span><\/label>\n                <select class=\"vc-select\" id=\"vc-profile\"><option value=\"machined\" selected>Machined (turning\/milling)<\/option><option value=\"ground\">Ground<\/option><option value=\"polished\">Polished\/Lapped<\/option><option value=\"cast\">Cast\/Forged<\/option><\/select><\/div>\n        <\/div>\n        <div class=\"vc-presets\"><div class=\"vc-presets-label\">Quick presets<\/div>\n            <button type=\"button\" class=\"vc-preset-btn\" data-ra=\"0.4\" data-p=\"ground\">Ground Ra 0.4<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-ra=\"1.6\" data-p=\"machined\">Turned Ra 1.6<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-ra=\"3.2\" data-p=\"machined\">Milled Ra 3.2<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-ra=\"12.5\" data-p=\"cast\">Cast Ra 12.5<\/button>\n        <\/div>\n    <\/form>\n    <div class=\"vc-results\" id=\"vc-results\">\n        <div class=\"vc-results-head\"><h2 class=\"vc-results-title\">Estimated Parameters<\/h2><button type=\"button\" class=\"vc-copy-btn\" id=\"vc-copy-btn\"><svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><rect x=\"9\" y=\"9\" width=\"13\" height=\"13\" rx=\"2\"\/><path d=\"M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1\"\/><\/svg> Copy<\/button><\/div>\n        <div class=\"vc-result-grid\">\n            <div class=\"vc-rcard vc-rcard-primary\"><div class=\"vc-rcard-label\">Ra (Arithmetical Mean)<\/div><div class=\"vc-rcard-value\" id=\"vc-r-ra\">\u2014<\/div><\/div>\n            <div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Rz (Max Height, est.)<\/div><div class=\"vc-rcard-value\" id=\"vc-r-rz\">\u2014<\/div><\/div>\n            <div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Rq (RMS, est.)<\/div><div class=\"vc-rcard-value\" id=\"vc-r-rq\">\u2014<\/div><\/div>\n            <div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Rt (Total Height, est.)<\/div><div class=\"vc-rcard-value\" id=\"vc-r-rt\">\u2014<\/div><\/div>\n            <div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Filter Cutoff \u03bbc<\/div><div class=\"vc-rcard-value\" id=\"vc-r-cutoff\">\u2014<\/div><\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<div class=\"vc-section vc-open\" id=\"vc-sec-theory\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"true\"><span class=\"vc-section-toggle-text\"><span class=\"vc-section-icon\">\ud83d\udcd8<\/span><span class=\"vc-section-title\">Theory &amp; Reference<\/span><\/span><svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg><\/button>\n    <div class=\"vc-section-body\"><div class=\"vc-section-inner vc-theory\">\n        <h3>Profile Parameters<\/h3>\n        <div class=\"vc-formula-box\" id=\"vc-katex-1\"><\/div>\n        <table class=\"vc-table\"><thead><tr><th>Parameter<\/th><th>Definition<\/th><th>Approx. Relation to Ra<\/th><\/tr><\/thead><tbody>\n            <tr><td><strong>Ra<\/strong><\/td><td>Arithmetical mean of |Z(x)| over evaluation length<\/td><td>1.0 \u00d7 Ra<\/td><\/tr>\n            <tr><td><strong>Rq<\/strong><\/td><td>Root mean square of Z(x)<\/td><td>1.11 \u00d7 Ra (Gaussian)<\/td><\/tr>\n            <tr><td><strong>Rz<\/strong><\/td><td>Max height: average of 5 highest peaks + 5 deepest valleys<\/td><td>4\u20137 \u00d7 Ra (process dependent)<\/td><\/tr>\n            <tr><td><strong>Rt<\/strong><\/td><td>Total height: max peak to min valley over full length<\/td><td>5\u201310 \u00d7 Ra<\/td><\/tr>\n        <\/tbody><\/table>\n        <h3>Default Filter Cutoff (\u03bbc)<\/h3>\n        <table class=\"vc-table\"><thead><tr><th>Ra Range (\u03bcm)<\/th><th>\u03bbc (mm)<\/th><th>Evaluation Length (mm)<\/th><\/tr><\/thead><tbody>\n            <tr><td>0.006 \u2013 0.02<\/td><td>0.08<\/td><td>0.4<\/td><\/tr>\n            <tr><td>0.02 \u2013 0.1<\/td><td>0.25<\/td><td>1.25<\/td><\/tr>\n            <tr><td>0.1 \u2013 2.0<\/td><td>0.8<\/td><td>4.0<\/td><\/tr>\n            <tr><td>2.0 \u2013 10<\/td><td>2.5<\/td><td>12.5<\/td><\/tr>\n            <tr><td>10 \u2013 80<\/td><td>8.0<\/td><td>40.0<\/td><\/tr>\n        <\/tbody><\/table>\n        <div class=\"vc-info-box\"><p><strong>Note:<\/strong> The Ra-to-Rz conversion is approximate and depends heavily on the machining process. Always measure directly when possible.<\/p><\/div>\n    <\/div><\/div>\n<\/div>\n<div class=\"vc-section\" id=\"vc-sec-related\"><button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\"><span class=\"vc-section-toggle-text\"><span class=\"vc-section-icon\">\ud83d\udd17<\/span><span class=\"vc-section-title\">Related Calculators<\/span><\/span><svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg><\/button><div class=\"vc-section-body\"><div class=\"vc-section-inner\"><div class=\"vc-related\"><a class=\"vc-related-link\" href=\"\/calculators\/surface-roughness-symbols\/\">Surface Roughness Symbols<\/a><a class=\"vc-related-link\" href=\"\/calculators\/general-tolerances-iso2768-2\/\">ISO 2768-2<\/a><\/div><\/div><\/div><\/div>\n<div class=\"vc-section\" id=\"vc-sec-faq\"><button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\"><span class=\"vc-section-toggle-text\"><span class=\"vc-section-icon\">\u2753<\/span><span class=\"vc-section-title\">Frequently Asked Questions<\/span><\/span><svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg><\/button><div class=\"vc-section-body\"><div class=\"vc-section-inner\"><div class=\"vc-faq-list\" id=\"vc-faq-list\"><\/div><\/div><\/div><\/div>\n<div class=\"vc-promo\"><div class=\"vc-promo-text\"><strong>Vibromera \u2014 Portable Balancing &amp; Vibration Analysis<\/strong><br>Professional instruments.<\/div><a class=\"vc-promo-link\" href=\"https:\/\/vibromera.eu\/\" target=\"_blank\" rel=\"noopener\">Learn More<\/a><\/div>\n<footer class=\"vc-footer\"><p>\u00a9 2024\u20132025 <a href=\"https:\/\/vibromera.eu\/\">Vibromera<\/a><\/p><p style=\"font-size:12px;margin-top:4px;\">Based on ISO 21920. Last updated: February 2025<\/p><div class=\"vc-footer-links\"><a href=\"\/calculators\/engineering-calculators\/\">All Calculators<\/a><a href=\"https:\/\/vibromera.eu\/contacts\/\">Contact<\/a><\/div><\/footer>\n<\/div>\n<script src=\"https:\/\/cdn.jsdelivr.net\/npm\/katex@0.16.11\/dist\/katex.min.js\"><\/script>\n<script>\n(function(){\n'use strict';var SLUG='surface-parameters-iso21920';function $(id){return document.getElementById(id);}function fmt(n,d){return isNaN(n)?'\u2014':n.toFixed(d===undefined?3:d);}\nvar RATIOS={machined:{rz:5.5,rq:1.11,rt:7.5},ground:{rz:5.0,rq:1.11,rt:7.0},polished:{rz:4.0,rq:1.11,rt:5.5},cast:{rz:6.5,rq:1.25,rt:9.0}};\nfunction getCutoff(ra){if(ra<=0.02)return{lc:0.08,ln:0.4};if(ra<=0.1)return{lc:0.25,ln:1.25};if(ra<=2)return{lc:0.8,ln:4.0};if(ra<=10)return{lc:2.5,ln:12.5};return{lc:8.0,ln:40.0};}\nfunction calculate(){var ra=parseFloat($('vc-ra').value);var prof=$('vc-profile').value;if(!ra||ra<=0){$('vc-results').classList.remove('vc-visible');return;}var r=RATIOS[prof];var rz=ra*r.rz;var rq=ra*r.rq;var rt=ra*r.rt;var co=getCutoff(ra);$('vc-r-ra').innerHTML=fmt(ra,3)+' <span class=\"vc-rcard-unit\">\u03bcm<\/span>';$('vc-r-rz').innerHTML='\u2248 '+fmt(rz,2)+' <span class=\"vc-rcard-unit\">\u03bcm<\/span> <span class=\"vc-rcard-unit\">('+fmt(r.rz,1)+'\u00d7 Ra)<\/span>';$('vc-r-rq').innerHTML='\u2248 '+fmt(rq,3)+' <span class=\"vc-rcard-unit\">\u03bcm<\/span> <span class=\"vc-rcard-unit\">('+fmt(r.rq,2)+'\u00d7 Ra)<\/span>';$('vc-r-rt').innerHTML='\u2248 '+fmt(rt,2)+' <span class=\"vc-rcard-unit\">\u03bcm<\/span> <span class=\"vc-rcard-unit\">('+fmt(r.rt,1)+'\u00d7 Ra)<\/span>';$('vc-r-cutoff').innerHTML=co.lc+' <span class=\"vc-rcard-unit\">mm<\/span> <span class=\"vc-rcard-unit\">(eval. length '+co.ln+' mm)<\/span>';$('vc-results').classList.add('vc-visible');saveHistory({ra:ra,profile:prof,_summary:'Ra '+ra+' \u03bcm \u2192 Rz\u2248'+fmt(rz,2)+' Rq\u2248'+fmt(rq,3)});}\ndocument.querySelectorAll('.vc-preset-btn').forEach(function(btn){btn.addEventListener('click',function(e){e.preventDefault();$('vc-ra').value=this.getAttribute('data-ra');$('vc-profile').value=this.getAttribute('data-p');calculate();});});\n$('vc-form').addEventListener('input',calculate);$('vc-form').addEventListener('change',calculate);\n$('vc-copy-btn').addEventListener('click',function(){var text='Surface Parameters (ISO 21920)\\n\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\\nRa: '+$('vc-r-ra').textContent+'\\nRz: '+$('vc-r-rz').textContent+'\\nRq: '+$('vc-r-rq').textContent+'\\nRt: '+$('vc-r-rt').textContent+'\\nCutoff: '+$('vc-r-cutoff').textContent+'\\n\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\\nvibromera.eu';if(navigator.clipboard){navigator.clipboard.writeText(text).then(function(){var b=$('vc-copy-btn');b.classList.add('vc-copied');b.innerHTML='<svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><polyline points=\"20 6 9 17 4 12\"\/><\/svg> Copied!';setTimeout(function(){b.classList.remove('vc-copied');b.innerHTML='<svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><rect x=\"9\" y=\"9\" width=\"13\" height=\"13\" rx=\"2\"\/><path d=\"M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1\"\/><\/svg> Copy';},2000);});}});\ndocument.querySelectorAll('.vc-section-toggle').forEach(function(btn){btn.addEventListener('click',function(){var s=this.closest('.vc-section');s.classList.toggle('vc-open');this.setAttribute('aria-expanded',s.classList.contains('vc-open'));});});\nvar faqData=[{q:'What is the difference between Ra and Rz?',a:'<p>Ra is the average deviation. Rz is the maximum height (average of 5 peak-to-valley measurements). Rz is typically 4\u20137\u00d7 Ra for machined surfaces.<\/p>'},{q:'What filter cutoff should I use?',a:'<p>Per ISO 21920 defaults: \u03bbc = 0.8 mm for Ra 0.1\u20132 \u03bcm, \u03bbc = 2.5 mm for Ra 2\u201310 \u03bcm. The evaluation length = 5 \u00d7 \u03bbc.<\/p>'},{q:'What is Rq?',a:'<p>Rq is root mean square roughness \u2014 the RMS of profile deviations. Rq \u2248 1.11 \u00d7 Ra for Gaussian profiles. More sensitive to peaks\/valleys than Ra.<\/p>'},{q:'What is Rt?',a:'<p>Rt is total height \u2014 max peak to min valley across the entire evaluation length. Rt \u2265 Rz always. Sensitive to scratches and defects.<\/p>'},{q:'How does ISO 21920 differ from ISO 4287?',a:'<p>ISO 21920 replaces and consolidates ISO 4287 and ISO 3274 into a single updated standard series for profile parameters.<\/p>'}];\nvar fl=$('vc-faq-list');faqData.forEach(function(f){fl.innerHTML+='<div class=\"vc-faq-item\"><button type=\"button\" class=\"vc-faq-q\"><span>'+f.q+'<\/span><svg class=\"vc-faq-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg><\/button><div class=\"vc-faq-a\"><div class=\"vc-faq-a-inner\">'+f.a+'<\/div><\/div><\/div>';});fl.addEventListener('click',function(e){var b=e.target.closest('.vc-faq-q');if(!b)return;b.closest('.vc-faq-item').classList.toggle('vc-open');});\nfunction saveHistory(e){var k='vc_history_'+SLUG;var a=[];try{a=JSON.parse(localStorage.getItem(k))||[];}catch(x){}e._ts=new Date().toISOString();a.unshift(e);if(a.length>10)a=a.slice(0,10);try{localStorage.setItem(k,JSON.stringify(a));}catch(x){}}\nfunction renderFormulas(){try{katex.render('Ra = \\\\frac{1}{l}\\\\int_0^l |Z(x)|\\\\,dx \\\\qquad Rq = \\\\sqrt{\\\\frac{1}{l}\\\\int_0^l Z(x)^2\\\\,dx}',$('vc-katex-1'),{displayMode:true,throwOnError:false});}catch(e){}}\nfunction init(){renderFormulas();calculate();}if(document.readyState==='loading'){document.addEventListener('DOMContentLoaded',init);}else{init();}\n})();\n<\/script>\n","protected":false},"excerpt":{"rendered":"<p>Gratis online kalkulator for ISO 21920-overflateprofilparametere. Skriv inn Ra-verdien for \u00e5 estimere Rz-, Rq- og Rt-forhold. Filtrer grenseverdier og parameterbeskrivelser.<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[],"tags":[],"class_list":["post-100250","calculator","type-calculator","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator\/100250","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator"}],"about":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/types\/calculator"}],"version-history":[{"count":2,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator\/100250\/revisions"}],"predecessor-version":[{"id":100762,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/calculator\/100250\/revisions\/100762"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/media?parent=100250"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/categories?post=100250"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/nb\/wp-json\/wp\/v2\/tags?post=100250"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}