{"id":100068,"date":"2026-02-15T20:14:47","date_gmt":"2026-02-15T20:14:47","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100068"},"modified":"2026-02-15T20:14:47","modified_gmt":"2026-02-15T20:14:47","slug":"coupling-unbalance-tolerance","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/bn\/calculators\/coupling-unbalance-tolerance\/","title":{"rendered":"\u0995\u09be\u09aa\u09b2\u09bf\u0982 \u0985\u09b8\u09be\u09ae\u099e\u09cd\u099c\u09b8\u09cd\u09af \u09b8\u09b9\u09a8\u09b6\u09c0\u09b2\u09a4\u09be \u0995\u09cd\u09af\u09be\u09b2\u0995\u09c1\u09b2\u09c7\u099f\u09b0 | ISO 21940 | \u09ac\u09bf\u09a8\u09be\u09ae\u09c2\u09b2\u09cd\u09af\u09c7 \u0985\u09a8\u09b2\u09be\u0987\u09a8 \u09b8\u09b0\u099e\u09cd\u099c\u09be\u09ae"},"content":{"rendered":"\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"Coupling Unbalance Tolerance Calculator\",\"alternateName\":[\"Coupling Balance Grade Calculator\"],\"description\":\"Calculate permissible coupling unbalance using ISO 21940 balance quality grades.\",\"url\":\"https:\/\/vibromera.eu\/calculators\/coupling-unbalance-tolerance\/\",\"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\":\"2025-02-14\",\"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\":\"Why do couplings need to be balanced?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Couplings rotate at shaft speed and any unbalance creates a centrifugal force proportional to mass \u00d7 eccentricity \u00d7 \u03c9\u00b2. Even small coupling unbalance can cause significant vibration at high speeds, especially in precision machinery.\"}},\n{\"@type\":\"Question\",\"name\":\"What balance grade should I use for couplings?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Most flexible couplings use G6.3 or G16. Precision couplings for turbomachinery may require G2.5 or G1.0. API 671 specifies that coupling unbalance should not exceed the lesser of the calculated ISO grade value or specific API limits.\"}},\n{\"@type\":\"Question\",\"name\":\"How is coupling unbalance different from rotor unbalance?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"The formula is identical \u2014 U = e \u00d7 m, where e = G\u00d71000\/\u03c9. However, coupling unbalance must be considered separately because it acts at the coupling location, which may amplify its effect depending on the distance to bearings.\"}},\n{\"@type\":\"Question\",\"name\":\"What is the API 671 coupling balance requirement?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"API 671 requires coupling components to be balanced individually to a level that the residual unbalance does not exceed 10W\/n (oz\u00b7in) or the ISO 21940-11 Grade G1.6 calculation, whichever is less. W = journal weight (lb), n = max speed (RPM).\"}},\n{\"@type\":\"Question\",\"name\":\"Should I balance a half-coupling or complete coupling?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Each half-coupling should be balanced individually, as the complete coupling may not always be assembled in the same orientation. Use the mass of each half-coupling for the calculation, then verify the assembled coupling balance.\"}}\n]}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"BreadcrumbList\",\"itemListElement\":[\n{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/vibromera.eu\/\"},\n{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Calculators\",\"item\":\"https:\/\/vibromera.eu\/calculators\/\"},\n{\"@type\":\"ListItem\",\"position\":3,\"name\":\"Coupling Unbalance Tolerance\",\"item\":\"https:\/\/vibromera.eu\/calculators\/coupling-unbalance-tolerance\/\"}\n]}\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 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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}\n@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-coupling-unbalance\">\n\n<header class=\"vc-header\">\n    <p class=\"vc-header-eyebrow\">Free Engineering Tool \u2014 #016<\/p>\n    <h1 class=\"vc-header-title\">Coupling Unbalance Tolerance Calculator<\/h1>\n    <p class=\"vc-header-subtitle\">Calculate the permissible unbalance for couplings using ISO 21940-11 balance quality grades. Enter coupling mass, maximum speed, and grade.<\/p>\n    <div class=\"vc-badges\"><span class=\"vc-badge\">ISO 21940-11<\/span><span class=\"vc-badge\">API 671<\/span><span class=\"vc-badge\">Couplings<\/span><\/div>\n<\/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\">\n                <label class=\"vc-label\" for=\"vc-mass\">Coupling Mass <span class=\"vc-label-hint\">(kg)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-mass\" inputmode=\"decimal\" step=\"any\" min=\"0.001\" placeholder=\"e.g. 15\" value=\"15\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-speed\">Maximum Speed <span class=\"vc-label-hint\">(RPM)<\/span><\/label>\n                <input class=\"vc-input\" type=\"number\" id=\"vc-speed\" inputmode=\"decimal\" step=\"any\" min=\"1\" placeholder=\"e.g. 3600\" value=\"3600\">\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-grade\">Balance Grade G<\/label>\n                <select class=\"vc-select\" id=\"vc-grade\">\n                    <option value=\"40\">G40 \u2014 General purpose couplings<\/option>\n                    <option value=\"16\">G16 \u2014 Standard flexible couplings<\/option>\n                    <option value=\"6.3\" selected>G6.3 \u2014 Precision couplings<\/option>\n                    <option value=\"2.5\">G2.5 \u2014 Turbomachinery couplings<\/option>\n                    <option value=\"1\">G1.0 \u2014 High-speed precision<\/option>\n                    <option value=\"0.4\">G0.4 \u2014 Ultra-precision<\/option>\n                <\/select>\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-halves\">Calculate For<\/label>\n                <select class=\"vc-select\" id=\"vc-halves\">\n                    <option value=\"full\" selected>Complete coupling<\/option>\n                    <option value=\"half\">Half-coupling (mass \/ 2)<\/option>\n                <\/select>\n            <\/div>\n        <\/div>\n        <div class=\"vc-presets\">\n            <div class=\"vc-presets-label\">Quick presets<\/div>\n            <button type=\"button\" class=\"vc-preset-btn\" data-m=\"8\" data-s=\"3600\" data-g=\"6.3\">Disc coupling 8 kg \/ 3600 RPM<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-m=\"25\" data-s=\"1800\" data-g=\"6.3\">Gear coupling 25 kg \/ 1800 RPM<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-m=\"5\" data-s=\"10000\" data-g=\"2.5\">Turbo coupling 5 kg \/ 10 kRPM<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-m=\"45\" data-s=\"1500\" data-g=\"16\">Large flex 45 kg \/ 1500 RPM<\/button>\n        <\/div>\n    <\/form>\n\n    <div class=\"vc-results\" id=\"vc-results\">\n        <div class=\"vc-results-head\">\n            <h2 class=\"vc-results-title\">Results<\/h2>\n            <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>\n        <\/div>\n        <div class=\"vc-result-grid\">\n            <div class=\"vc-rcard vc-rcard-primary\">\n                <div class=\"vc-rcard-label\">Permissible Coupling Unbalance<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-ubal\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Specific Unbalance (Eccentricity)<\/div><div class=\"vc-rcard-value\" id=\"vc-r-ecc\">\u2014<\/div><\/div>\n            <div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Angular Velocity \u03c9<\/div><div class=\"vc-rcard-value\" id=\"vc-r-omega\">\u2014<\/div><\/div>\n            <div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Balance Grade<\/div><div class=\"vc-rcard-value\" id=\"vc-r-grade\">\u2014<\/div><\/div>\n            <div class=\"vc-rcard\"><div class=\"vc-rcard-label\">Effective Mass Used<\/div><div class=\"vc-rcard-value\" id=\"vc-r-mass\">\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\">\n        <span class=\"vc-section-toggle-text\"><span class=\"vc-section-icon\">\ud83d\udcd8<\/span><span class=\"vc-section-title\">Theory &amp; Formulas<\/span><\/span>\n        <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>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner vc-theory\">\n            <h3>Permissible Coupling Unbalance<\/h3>\n            <p>The same ISO 21940-11 formula applies to couplings:<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-1\"><\/div>\n            <div class=\"vc-formula-box\" id=\"vc-katex-2\"><\/div>\n            <ul>\n                <li><strong>G<\/strong> \u2014 balance quality grade (mm\/s)<\/li>\n                <li><strong>\u03c9<\/strong> \u2014 angular velocity = 2\u03c0 \u00d7 n \/ 60 (rad\/s)<\/li>\n                <li><strong>m<\/strong> \u2014 coupling mass (kg)<\/li>\n            <\/ul>\n\n            <h3>API 671 Requirement<\/h3>\n            <p>For special-purpose couplings per API 671, the permissible unbalance of each coupling component shall not exceed:<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-3\"><\/div>\n            <p>Where W is the journal static weight in pounds and n is max continuous speed in RPM.<\/p>\n\n            <h3>Practical Example<\/h3>\n            <div class=\"vc-example-box\">\n                <div class=\"vc-example-title\">Example \u2014 Disc Coupling<\/div>\n                <p><strong>Given:<\/strong> Coupling mass = 15 kg, Speed = 3600 RPM, Grade = G6.3<\/p>\n                <p>\u03c9 = 2\u03c0 \u00d7 3600 \/ 60 = 376.99 rad\/s<\/p>\n                <p>e<sub>per<\/sub> = 6.3 \u00d7 1000 \/ 376.99 = <strong>16.71 \u03bcm<\/strong><\/p>\n                <p>U<sub>per<\/sub> = 16.71 \u00d7 15 = <strong>250.7 g\u00b7mm<\/strong><\/p>\n            <\/div>\n\n            <div class=\"vc-warning-box\">\n                <p style=\"margin:0;font-size:14px;color:var(--vc-ink-secondary);\"><strong>\u26a0\ufe0f Note:<\/strong> For half-coupling balancing, use half the total coupling mass. Always verify assembled coupling balance after installation.<\/p>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<div class=\"vc-section\" id=\"vc-sec-related\">\n    <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>\n    <div class=\"vc-section-body\"><div class=\"vc-section-inner\"><div class=\"vc-related\">\n        <a class=\"vc-related-link\" href=\"\/calculators\/residual-unbalance-iso1940\/\">Residual Unbalance (ISO 21940)<\/a>\n        <a class=\"vc-related-link\" href=\"\/calculators\/flexible-rotor-balancing\/\">Flexible Rotor Balancing<\/a>\n        <a class=\"vc-related-link\" href=\"\/calculators\/vibration-velocity\/\">Vibration Velocity (ISO 10816)<\/a>\n        <a class=\"vc-related-link\" href=\"\/calculators\/trial-weight-calculator\/\">Trial Weight Calculator<\/a>\n    <\/div><\/div><\/div>\n<\/div>\n\n<div class=\"vc-section\" id=\"vc-sec-faq\">\n    <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>\n    <div class=\"vc-section-body\"><div class=\"vc-section-inner\"><div class=\"vc-faq-list\" id=\"vc-faq-list\"><\/div><\/div><\/div>\n<\/div>\n\n<div class=\"vc-promo\"><div class=\"vc-promo-text\"><strong>Vibromera \u2014 Portable Balancing &amp; Vibration Analysis<\/strong><br>Balance couplings and rotors on-site with professional portable instruments. ISO 21940-11 compliance. Used in 50+ countries.<\/div><a class=\"vc-promo-link\" href=\"https:\/\/vibromera.eu\/\" target=\"_blank\" rel=\"noopener\">Learn More<\/a><\/div>\n\n<footer class=\"vc-footer\">\n    <p>\u00a9 2024\u20132025 <a href=\"https:\/\/vibromera.eu\/\">Vibromera<\/a> \u2014 Engineering Calculators<\/p>\n    <p style=\"font-size:12px;margin-top:4px;\">Based on ISO 21940-11 applied to coupling components. Last updated: February 2025<\/p>\n    <div class=\"vc-footer-links\"><a href=\"\/calculators\/engineering-calculators\/\">All Calculators<\/a><a href=\"https:\/\/vibromera.eu\/contacts\/\">Contact<\/a><\/div>\n<\/footer>\n\n<\/div>\n\n<script src=\"https:\/\/cdn.jsdelivr.net\/npm\/katex@0.16.11\/dist\/katex.min.js\"><\/script>\n<script>\n(function(){\n    'use strict';\n    var SLUG='coupling-unbalance-tolerance';\n    function $(id){return document.getElementById(id)}\n    function fmt(n,d){if(isNaN(n)||!isFinite(n))return '\u2014';var f=n.toFixed(d===undefined?2:d);return f.replace(\/(\\.\\d*?)0+$\/,'$1').replace(\/\\.$\/,'')}\n\n    function calculate(){\n        var mass=parseFloat($('vc-mass').value);\n        var speed=parseFloat($('vc-speed').value);\n        var grade=parseFloat($('vc-grade').value);\n        var halves=$('vc-halves').value;\n        if(!mass||mass<=0||!speed||speed<=0){$('vc-results').classList.remove('vc-visible');return}\n\n        var effMass=halves==='half'?mass\/2:mass;\n        var omega=2*Math.PI*speed\/60;\n        var eper=grade*1000\/omega;\n        var uper=eper*effMass;\n\n        $('vc-r-ubal').innerHTML=(uper>=1000?fmt(uper,0):fmt(uper,1))+' <span class=\"vc-rcard-unit\">g\u00b7mm<\/span>';\n        $('vc-r-ecc').innerHTML=fmt(eper,2)+' <span class=\"vc-rcard-unit\">\u03bcm<\/span>';\n        $('vc-r-omega').innerHTML=fmt(omega,2)+' <span class=\"vc-rcard-unit\">rad\/s<\/span>';\n        $('vc-r-grade').innerHTML='G'+grade;\n        $('vc-r-mass').innerHTML=fmt(effMass,2)+' <span class=\"vc-rcard-unit\">kg<\/span>'+(halves==='half'?' <span class=\"vc-rcard-unit\">(half)<\/span>':'');\n        $('vc-results').classList.add('vc-visible');\n\n        saveHistory({mass:mass,speed:speed,grade:grade,uper:fmt(uper,1),_summary:'m='+effMass+'kg, n='+speed+'RPM, G'+grade+' \u2192 '+fmt(uper,1)+' g\u00b7mm'});\n    }\n\n    document.querySelectorAll('.vc-preset-btn').forEach(function(btn){btn.addEventListener('click',function(e){e.preventDefault();$('vc-mass').value=this.getAttribute('data-m');$('vc-speed').value=this.getAttribute('data-s');$('vc-grade').value=this.getAttribute('data-g');calculate()})});\n    $('vc-form').addEventListener('input',calculate);\n    $('vc-form').addEventListener('change',calculate);\n\n    $('vc-copy-btn').addEventListener('click',function(){\n        var text='Coupling Unbalance Tolerance\\n\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\\nMass: '+$('vc-mass').value+' kg\\nSpeed: '+$('vc-speed').value+' RPM\\nGrade: G'+$('vc-grade').value+'\\nPermissible Unbalance: '+$('vc-r-ubal').textContent+'\\nEccentricity: '+$('vc-r-ecc').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\/calculators\/coupling-unbalance-tolerance\/';\n        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)})}\n    });\n\n    document.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'))})});\n\n    var faqData=[\n        {q:'Why do couplings need to be balanced?',a:'<p>Couplings rotate at shaft speed and any unbalance creates centrifugal force proportional to mass \u00d7 eccentricity \u00d7 \u03c9\u00b2. Even small coupling unbalance causes significant vibration at high speeds.<\/p>'},\n        {q:'What balance grade should I use for couplings?',a:'<p>G6.3 for standard precision couplings. G2.5 for turbomachinery. G16 for general-purpose flexible couplings. API 671 may impose stricter limits for special-purpose applications.<\/p>'},\n        {q:'How is coupling unbalance different from rotor unbalance?',a:'<p>The ISO formula is identical. However, coupling unbalance acts at the coupling location and may be amplified depending on distance to bearings and the mode shapes of the rotor system.<\/p>'},\n        {q:'What is the API 671 coupling balance requirement?',a:'<p>API 671 requires each coupling component\\'s residual unbalance not to exceed 10W\/n (oz\u00b7in), where W = journal static weight (lb) and n = max continuous speed (RPM), or ISO G1.6, whichever is less.<\/p>'},\n        {q:'Should I balance a half-coupling or complete coupling?',a:'<p>Balance each half-coupling individually since assembly orientation may vary. Use half the total coupling mass for calculation. 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