{"id":66907,"date":"2026-10-13T10:10:58","date_gmt":"2026-10-13T07:10:58","guid":{"rendered":"https:\/\/wpcalc.com\/en\/?p=66907"},"modified":"2026-10-13T10:10:58","modified_gmt":"2026-10-13T07:10:58","slug":"photon-energy-calculator","status":"publish","type":"post","link":"https:\/\/wpcalc.com\/en\/chemistry\/photon-energy-calculator\/","title":{"rendered":"Photon Energy 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\">Photon Energy from Wavelength or Frequency<\/h2><\/div><div class=\"calcdash-favorite group\">\n  <button type=\"button\" class=\"favorite\" id=\"favorite\" data-favorite-id=\"66907\" data-favorite-title=\"Photon Energy\" data-favorite-url=\"https:\/\/wpcalc.com\/en\/chemistry\/photon-energy-calculator\/\" data-favorite-excerpt=\"Calculate the energy of a photon from its wavelength or frequency. Enter either value and get the energy per photon in joules and electronvolts, plus the energy per mole of photons in kJ\/mol.\" aria-label=\"Add to Favorites\" data-favorite-icon=\"icon icon-spectrum\">\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\/chemistry\/photon-energy-calculator\/\" method=\"POST\" class=\"calculator\" id=\"calculator-66907\" data-post=\"66907\"><fieldset class=\"fieldset-input is-2\"><legend class=\"sr-only\">Input Fields<\/legend><div class=\"field\" id=\"input-1\"><label for=\"field-1\">Input Type<\/label><div class=\"grid grid-cols-1\"><select id=\"field-1\" name=\"input_type\"><option value=\"wl\" selected>Wavelength (\u03bb)<\/option><option value=\"fr\">Frequency (\u03bd)<\/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><div class=\"field is-single has-term\" id=\"input-2\"><label for=\"field-2\">Wavelength (\u03bb)<\/label><div class=\"term\">\u03bb<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><div class=\"field-group\"><input type=\"text\" name=\"wavelength_\" id=\"field-2\" aria-describedby=\"calc-info-2\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 500\" min=\"0\" value=\"500\"\/><div class=\"grid grid-cols-1\"><select id=\"field-3\" name=\"unit\" aria-label=\"Unit\"><option value=\"nm\" selected>nm<\/option><option value=\"um\">\u00b5m<\/option><option value=\"mm\">mm<\/option><option value=\"cm\">cm<\/option><option value=\"m\">m<\/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><small id=\"calc-info-2\">Wavelength of the light in vacuum.<\/small><\/div><div class=\"field is-single has-term\" id=\"input-3\" hidden><label for=\"field-4\">Frequency (\u03bd)<\/label><div class=\"term\">\u03bd<\/div>  <div class=\"absolute bottom-0 left-16 top-8 w-2 h-0.5 bg-blue-500\"><\/div><div class=\"field-group\"><input type=\"text\" name=\"frequency_\" id=\"field-4\" aria-describedby=\"calc-info-4\" data-number inputmode=\"decimal\" autocomplete=\"off\" spellcheck=\"false\" placeholder=\"e.g. 600\" min=\"0\" value=\"600\"\/><div class=\"grid grid-cols-1\"><select id=\"field-5\" name=\"unit\" aria-label=\"Unit\"><option value=\"hz\">Hz<\/option><option value=\"khz\">kHz<\/option><option value=\"mhz\">MHz<\/option><option value=\"ghz\">GHz<\/option><option value=\"thz\" selected>THz<\/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><small id=\"calc-info-4\">Frequency of the light (cycles per second).<\/small><\/div><\/fieldset><div class=\"buttons\"><button type=\"submit\" data-text=\"Re-Calculate\" id=\"calculate-button\" data-post=\"66907\">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> Photon Energy<\/h3><div class=\"result-box\"><div class=\"field-result\" id=\"output-1\"><span class=\"field-title\"><span>Energy per Photon<\/span><span class=\"result-term\">E<\/span><\/span><span class=\"field-value\" id=\"result-1\" data-unit=\"J\"><\/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 class=\"field-result\" id=\"output-2\"><span class=\"field-title\"><span>Energy per Photon<\/span><span class=\"result-term\">E<\/span><\/span><span class=\"field-value\" id=\"result-2\" data-unit=\"eV\"><\/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 class=\"field-result\" id=\"output-3\"><span class=\"field-title\"><span>Energy per Mole of Photons<\/span><span class=\"result-term\">E\u00b7N_A<\/span><\/span><span class=\"field-value\" id=\"result-3\" data-unit=\"kJ\/mol\"><\/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 class=\"field-result\" id=\"output-4\"><span class=\"field-title\"><span>Frequency<\/span><span class=\"result-term\">\u03bd<\/span><\/span><span class=\"field-value\" id=\"result-4\"><\/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 class=\"field-result\" id=\"output-5\"><span class=\"field-title\"><span>Wavelength<\/span><span class=\"result-term\">\u03bb<\/span><\/span><span class=\"field-value\" id=\"result-5\"><\/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 class=\"field-result is-column\" id=\"output-6\"><span class=\"field-title\"><span>Calculation Details<\/span><\/span><span class=\"field-value\" id=\"result-6\"><\/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 class=\"field-result is-column\" id=\"output-7\"><span class=\"field-title\"><span>About Photon Energy<\/span><\/span><span class=\"field-value\" id=\"result-7\"><\/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=\"66907\" aria-live=\"polite\" 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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>Photon Energy<\/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\\[ E = h\\nu = \\frac{hc}{\\lambda} \\qquad \\nu = \\frac{c}{\\lambda} \\qquad E_{\\text{mol}} = E \\cdot N_A \\]\n<\/div>\r\n\t<\/figure>\r\n\t<\/p>\n<p><strong>Where:<\/strong><\/p>\n<ul>\n<li>\\(E\\) \u2014 energy of one photon (J)<\/li>\n<li>\\(h\\) \u2014 Planck constant, \\(6.62607015 \\times 10^{-34}\\) J\u00b7s (exact)<\/li>\n<li>\\(\\nu\\) \u2014 frequency of the light (Hz)<\/li>\n<li>\\(c\\) \u2014 speed of light in vacuum, \\(2.99792458 \\times 10^{8}\\) m\/s (exact)<\/li>\n<li>\\(\\lambda\\) \u2014 wavelength in vacuum (m)<\/li>\n<li>\\(N_A\\) \u2014 Avogadro constant, \\(6.02214076 \\times 10^{23}\\) mol\u207b\u00b9 (exact)<\/li>\n<li>\\(E_{\\text{mol}}\\) \u2014 energy per mole of photons, also called one einstein (J\/mol)<\/li>\n<\/ul>\n<p>This is the Planck relation: the energy of a single photon is fixed entirely by the frequency (or equivalently the wavelength) of the light, because \\(\\lambda \\nu = c\\).<\/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>Photon Energy \u2013 Calculation Example<\/h2><\/div>\r\n\r\n<\/p>\n<p><strong>Example:<\/strong> green light with a wavelength of 500 nm (the calculator's default value).<\/p>\n<p>\\[ \\lambda = 500\\ \\text{nm} = 5.00 \\times 10^{-7}\\ \\text{m} \\]<\/p>\n<p>\\[ \\nu = \\frac{c}{\\lambda} = \\frac{2.99792458 \\times 10^{8}}{5.00 \\times 10^{-7}} = 5.996 \\times 10^{14}\\ \\text{Hz} \\approx 599.6\\ \\text{THz} \\]<\/p>\n<p>\\[ E = h\\nu = 6.62607015 \\times 10^{-34} \\times 5.996 \\times 10^{14} = 3.973 \\times 10^{-19}\\ \\text{J} \\]<\/p>\n<p>\\[ E = \\frac{3.973 \\times 10^{-19}}{1.602176634 \\times 10^{-19}} \\approx 2.48\\ \\text{eV} \\qquad E_{\\text{mol}} = 3.973 \\times 10^{-19} \\times 6.02214076 \\times 10^{23} \\approx 239\\ \\text{kJ\/mol} \\]<\/p>\n<p><strong>Result:<\/strong> each photon of 500 nm light carries \\(3.973 \\times 10^{-19}\\) J \u2248 2.48 eV, and one mole of such photons carries about 239 kJ. This lies in the green region of the visible spectrum.<\/p>\n<p>\n\r\n<\/section>\n<h2>How to Use the Calculator<\/h2>\n<ol>\n<li>In the <strong>Input Type<\/strong> dropdown, select <strong>Wavelength (\u03bb)<\/strong> or <strong>Frequency (\u03bd)<\/strong>, depending on which quantity you know.<\/li>\n<li>If you chose wavelength, enter the value in the <strong>Wavelength (\u03bb)<\/strong> field and pick the unit (nm, \u00b5m, mm, cm or m). If you chose frequency, enter the value in the <strong>Frequency (\u03bd)<\/strong> field and pick the unit (Hz, kHz, MHz, GHz or THz).<\/li>\n<li>The result panel shows the <strong>Energy per Photon<\/strong> in joules and electronvolts, the <strong>Energy per Mole of Photons<\/strong> in kJ\/mol, plus the complementary wavelength or frequency and the wavenumber in cm\u207b\u00b9.<\/li>\n<li>Check the <strong>Calculation Details<\/strong> panel for the step-by-step computation and the <strong>About Photon Energy<\/strong> panel for context on the spectral region and typical benchmarks.<\/li>\n<\/ol>\n<h2>What Is Photon Energy?<\/h2>\n<p>Light behaves both as a wave and as a stream of particles called photons. Each photon carries a tiny, discrete packet of energy whose size depends only on the light's frequency: higher frequency (shorter wavelength) means more energetic photons. This is the essence of the Planck relation \\(E = h\\nu\\), the equation that launched quantum physics in 1900 and later earned Einstein's explanation of the photoelectric effect a Nobel Prize.<\/p>\n<p>A single photon's energy is extremely small \u2014 around \\(10^{-19}\\) J for visible light \u2014 so it is usually quoted in <strong>electronvolts (eV)<\/strong>, where 1 eV is the energy an electron gains crossing a 1-volt potential (\\(1\\ \\text{eV} = 1.602 \\times 10^{-19}\\) J). Visible photons span roughly 1.6 eV (750 nm, red) to 3.3 eV (380 nm, violet); UV photons are more energetic still, and gamma-ray photons reach millions of eV.<\/p>\n<p>In chemistry and photochemistry the <strong>energy per mole of photons<\/strong> (one einstein) is often the more useful figure, because it lets you compare photon energy directly with bond energies and activation energies in kJ\/mol. For example, 254 nm UV light delivers about 471 kJ\/mol \u2014 enough to break many covalent bonds \u2014 while 700 nm red light delivers only about 171 kJ\/mol, below even the weakest O\u2013O single bonds. This is why UV light causes sunburn and photodegradation while red light generally does not.<\/p>\n<p>Note that photon energy depends only on the color (wavelength) of the light, never on its brightness. Intensity determines <em>how many<\/em> photons arrive per second; each individual photon always carries exactly \\(h\\nu\\). If you are combining light energies with bond energies to estimate reaction enthalpies, our <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/reaction-enthalpy-from-bond-energies-calculator\/\">Reaction Enthalpy from Bond Energies calculator<\/a> is a natural companion tool.<\/p>\n<h2>Reference Values<\/h2>\n<table>\n<thead>\n<tr>\n<th>Wavelength<\/th>\n<th>Region<\/th>\n<th>Energy (eV)<\/th>\n<th>Energy (kJ\/mol)<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>200 nm<\/td>\n<td>Far UV<\/td>\n<td>6.20<\/td>\n<td>598<\/td>\n<\/tr>\n<tr>\n<td>254 nm<\/td>\n<td>UV (Hg lamp)<\/td>\n<td>4.89<\/td>\n<td>471<\/td>\n<\/tr>\n<tr>\n<td>350 nm<\/td>\n<td>Near UV<\/td>\n<td>3.54<\/td>\n<td>342<\/td>\n<\/tr>\n<tr>\n<td>450 nm<\/td>\n<td>Visible (blue)<\/td>\n<td>2.76<\/td>\n<td>266<\/td>\n<\/tr>\n<tr>\n<td>500 nm<\/td>\n<td>Visible (green)<\/td>\n<td>2.48<\/td>\n<td>239<\/td>\n<\/tr>\n<tr>\n<td>700 nm<\/td>\n<td>Visible (red edge)<\/td>\n<td>1.77<\/td>\n<td>171<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Assumptions and Limitations<\/h2>\n<ul>\n<li>The calculation assumes the light travels in <strong>vacuum<\/strong>. For air the difference is negligible \u2014 the speed of light in air is only about 0.03% lower than in vacuum, which changes the wavelength-to-frequency mapping imperceptibly for most purposes.<\/li>\n<li>The constants \\(h\\), \\(c\\) and \\(N_A\\) are the exact SI 2019 values, so the only source of imprecision is the input itself.<\/li>\n<li>Wavelength and frequency must refer to the same medium; mixing a vacuum wavelength with an in-medium frequency would introduce an error equal to the refractive index.<\/li>\n<li>The calculator treats light as single photons. Effects such as multiphoton absorption (where two lower-energy photons are absorbed together) are nonlinear processes not covered by the simple Planck relation.<\/li>\n<li>When comparing with bond energies, remember that a photon must supply <em>at least<\/em> the bond dissociation energy in a single absorption event; surplus energy appears as kinetic energy, heat or fluorescence.<\/li>\n<\/ul>\n<p>If you work with the wave nature of light instead \u2014 for example diffraction by crystals \u2014 you may also find our <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/braggs-law-calculator\/\">Bragg's Law calculator<\/a> useful for relating wavelength to diffraction angles, or the <a href=\"https:\/\/wpcalc.com\/en\/chemistry\/standard-cell-potential-calculator\/\">Standard Cell Potential calculator<\/a> when converting between electrochemical voltages and electron energies in eV.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Calculate the energy of a photon from its wavelength or frequency. Enter either value and get the energy per photon in joules and electronvolts, plus the energy per mole of photons in kJ\/mol.<\/p>\n","protected":false},"author":3168,"featured_media":0,"comment_status":"open","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[54],"tags":[59],"class_list":["post-66907","post","type-post","status-publish","format-standard","hentry","category-chemistry","tag-spectrophotometry"],"acf":[],"_links":{"self":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66907","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\/3168"}],"replies":[{"embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/comments?post=66907"}],"version-history":[{"count":1,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66907\/revisions"}],"predecessor-version":[{"id":66908,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/posts\/66907\/revisions\/66908"}],"wp:attachment":[{"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/media?parent=66907"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/categories?post=66907"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpcalc.com\/en\/wp-json\/wp\/v2\/tags?post=66907"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}