{"id":64530,"date":"2025-05-12T10:07:54","date_gmt":"2025-05-12T07:07:54","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=64530"},"modified":"2026-09-30T18:36:38","modified_gmt":"2026-09-30T15:36:38","slug":"straight-wire-inductor","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/engineering\/straight-wire-inductor\/","title":{"rendered":"Straight Wire Inductor 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\">Inductance Estimator for Straight Round Conductors<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"64530\" data-favorite-title=\"Straight Wire Inductance\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/engineering\/straight-wire-inductor\/\" data-favorite-excerpt=\"Estimate the inductance of a straight round wire from its length and diameter. Useful for RF circuits, antenna elements, lead wires, and bus bars where even short conductors add reactance.\" aria-label=\"Add to Favorites\" data-favorite-icon=\"icon icon-magnet\">\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\/engineering\/straight-wire-inductor\/\" method=\"POST\" class=\"calculator\" id=\"calculator-64530\" data-post=\"64530\"><fieldset class=\"fieldset-input\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field has-term\" id=\"input-1\"><label for=\"field-1\">Wire Length<\/label><div class=\"term\">a<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"wire_length\" id=\"field-1\" aria-describedby=\"calc-unit-1 calc-info-1\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0.01\" value=\"10\"\/><div class=\"unit\" id=\"calc-unit-1\">cm<\/div><small id=\"calc-info-1\">Length of the wire<\/small><\/div><div class=\"field has-term\" id=\"input-2\"><label for=\"field-2\">Wire Diameter<\/label><div class=\"term\">d<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><input type=\"text\" name=\"wire_diameter\" id=\"field-2\" aria-describedby=\"calc-unit-2 calc-info-2\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" min=\"0.001\" value=\"0.1\"\/><div class=\"unit\" id=\"calc-unit-2\">cm<\/div><small id=\"calc-info-2\">Diameter of the wire<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"64530\">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>Inductance<\/span><\/span><span class=\"field-value\" id=\"result-1\" data-unit=\"\u00b5H\"><\/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=\"64530\" 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\">1<\/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>Straight Wire Inductance 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\\[ L = 0.00508\\,a\\left( \\log_{10}\\!\\left( \\frac{2a}{d} \\right) - 0.75 \\right) \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(L\\) \u2014 inductance of the wire (\u00b5H)<\/li>\n<li>\\(a\\) \u2014 length of the wire (cm)<\/li>\n<li>\\(d\\) \u2014 diameter of the wire (cm)<\/li>\n<\/ul>\n<p>This empirical formula approximates the inductance of a straight round conductor in free air. It is often written in the equivalent form \\(L = 0.002\\,a\\left[\\ln\\!\\left(\\frac{4a}{d}\\right) - 1\\right]\\) in \u00b5H with \\(a\\) and \\(d\\) in cm; both give nearly identical results for thin, straight wires.<\/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>Straight Wire Inductance \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> a straight copper wire is 10 cm long and has a diameter of 0.1 cm (about 1 mm, roughly AWG 18).<\/p>\n<p>\\[ L = 0.00508 \\times 10 \\times \\left( \\log_{10}\\!\\left( \\frac{2 \\times 10}{0.1} \\right) - 0.75 \\right) \\]<\/p>\n<p>\\[ L = 0.0508 \\times \\left( \\log_{10}(200) - 0.75 \\right) = 0.0508 \\times (2.3010 - 0.75) \\]<\/p>\n<p>\\[ L \\approx 0.0508 \\times 1.5510 \\approx 0.0788~\\mu\\mathrm{H} \\]<\/p>\n<p><strong>Result:<\/strong> the wire has an inductance of approximately 0.079 \u00b5H (79 nH).<\/p>\n<p>\n\r\n<\/section>\n<h2>How to Use the Calculator<\/h2>\n<ol>\n<li>Enter the <strong>Wire Length<\/strong> in centimeters \u2014 the end-to-end length of the straight conductor.<\/li>\n<li>Enter the <strong>Wire Diameter<\/strong> in centimeters \u2014 the diameter of the round cross-section, not the radius. If you only know the wire gauge, convert it to a diameter first (see the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/wire-gauge\/\">Wire Gauge calculator<\/a>).<\/li>\n<li>Read the <strong>Inductance<\/strong> result in microhenries (\u00b5H). For typical lead wires the value is small, so you may prefer to read it as nanohenries (1 \u00b5H = 1000 nH).<\/li>\n<\/ol>\n<p>The calculator requires \\(a &gt; 0\\), \\(d &gt; 0\\), and \\(2a &gt; d\\). The last condition reflects the fact that the formula is only meaningful for a wire that is long compared to its thickness; a stubby cylinder is not a \"straight wire\" in the sense of this model.<\/p>\n<h2>What Is the Inductance of a Straight Wire?<\/h2>\n<p>Any current-carrying conductor is surrounded by a magnetic field, and that field stores energy. A changing current therefore meets an opposing voltage \u2014 this is inductance. It is tempting to think of inductance as something that only coils have, but even a perfectly straight piece of wire possesses a small amount of it. The value depends mostly on the wire's length and, more weakly, on its thickness: longer wires have more inductance, and thicker wires have slightly less, because the magnetic flux loops around a fat conductor enclose less length per turn.<\/p>\n<p>The numbers are small but far from negligible in the right context. A 10 cm wire of 1 mm diameter \u2014 roughly the length of a component lead or a jumper \u2014 contributes about 79 nH, as in the example above. At 100 MHz that translates into a reactance of \\(X_L = 2\\pi f L \\approx 50~\\Omega\\), which can completely dominate a circuit's intended impedance. This is why RF layouts obsess over short, direct traces, and why a \"ground wire\" a few centimeters long is no longer a good ground at high frequencies.<\/p>\n<p>Typical figures to keep in mind: a 1 cm wire adds roughly 7\u201310 nH, and standard through-hole component leads (about 1 cm each, 0.5 mm diameter) contribute several nH per lead. When datasheets for RF components specify layouts with minimal lead length, this parasitic inductance is exactly what they are guarding against.<\/p>\n<p>This calculator is most useful when estimating parasitic inductance of: antenna elements and radials, jumper and lead wires, bus bars in power electronics, and bonding wires in prototypes. If you are designing transmission lines instead, the geometry of both conductors matters \u2014 see the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/parallel-wire-impedance\/\">Parallel Wire Impedance calculator<\/a> for the two-wire line case, or the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/microstrip-pcb-impedance\/\">Microstrip PCB Impedance calculator<\/a> for traces over a ground plane.<\/p>\n<h2>Assumptions, Limitations and Practical Tips<\/h2>\n<ul>\n<li><strong>Round conductor in free air.<\/strong> The formula assumes a straight wire of circular cross-section, far from other conductors and from magnetic or conductive materials. Nearby metal (a chassis, a ground plane) or insulation changes the field distribution and the actual inductance.<\/li>\n<li><strong>Thin-wire approximation.<\/strong> Accuracy is best when \\(a \\gg d\\). The formula becomes inaccurate as the wire approaches its own length in thickness; hence the \\(2a &gt; d\\) requirement in the calculator.<\/li>\n<li><strong>Low frequency \/ uniform current.<\/strong> At high frequencies the skin effect pushes current toward the surface, slightly reducing internal inductance. The external inductance \u2014 which dominates for thin wires \u2014 is barely affected, so the formula remains a good first estimate well into the VHF range.<\/li>\n<li><strong>No proximity or mutual effects.<\/strong> The result applies to a single isolated wire. Two parallel wires couple magnetically; if their fields partially cancel (as in a tightly twisted pair or a coaxial return), the net inductance is much lower than the sum of the individual wires.<\/li>\n<li><strong>Expect a few percent of uncertainty.<\/strong> This is an empirical engineering formula, not an exact solution. For sign-off on critical RF designs, verify with a field solver or measurement \u2014 but for estimating whether a lead is \"a few nH or a few dozen nH,\" it is entirely adequate.<\/li>\n<\/ul>\n<p>A practical rule: to minimize parasitic inductance, keep current paths short, use the widest conductor practical, and route the return current directly alongside the outgoing current so their magnetic fields cancel. When several inductances combine in a circuit, the <a href=\"https:\/\/wpcalc.com\/en\/engineering\/series-inductance\/\">Series Inductance<\/a> and <a href=\"https:\/\/wpcalc.com\/en\/engineering\/parallel-inductance\/\">Parallel Inductance<\/a> calculators can help you total them up.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Estimate the inductance of a straight round wire from its length and diameter. Useful for RF circuits, antenna elements, lead wires, and bus bars where even short conductors add reactance.<\/p>\n","protected":false},"author":70,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[4],"tags":[93],"class_list":["post-64530","post","type-post","status-publish","format-standard","hentry","category-engineering","tag-coils-transformers"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/64530","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=64530"}],"version-history":[{"count":4,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/64530\/revisions"}],"predecessor-version":[{"id":66019,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/64530\/revisions\/66019"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=64530"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=64530"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=64530"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}