{"id":2387,"date":"2026-02-10T00:00:01","date_gmt":"2026-02-09T22:00:01","guid":{"rendered":"https:\/\/science-x.net\/?page_id=2387"},"modified":"2026-02-10T00:00:02","modified_gmt":"2026-02-09T22:00:02","slug":"black-hole-radius-calculator","status":"publish","type":"page","link":"https:\/\/science-x.net\/?page_id=2387","title":{"rendered":"Black Hole Radius Calculator"},"content":{"rendered":"\n<div class=\"eco-tool wp-block-group\" id=\"eco-tool-bh-55a1c\">\n  <div class=\"eco-tool__header\">\n    <h2 class=\"eco-tool__title\">Black Hole Radius Calculator<\/h2>\n    <p class=\"eco-tool__lead\">\n      Calculate the Schwarzschild radius (event horizon) for a non-rotating black hole from its mass.\n    <\/p>\n  <\/div>\n\n  <form class=\"eco-tool__form\" id=\"eco-bh-form-55a1c\" novalidate>\n    <div class=\"eco-tool__grid3\">\n      <!-- Preset -->\n      <div class=\"eco-tool__field\">\n        <label class=\"eco-tool__label\" for=\"eco-bh-preset-55a1c\">\n          Preset<br>mass\n        <\/label>\n        <select class=\"eco-tool__input\" id=\"eco-bh-preset-55a1c\">\n          <option value=\"custom\" selected>Custom<\/option>\n          <option value=\"earth\">Earth mass (1 M\u2295)<\/option>\n          <option value=\"sun\">Sun mass (1 M\u2609)<\/option>\n          <option value=\"sgrA\">Sagittarius A* (~4.0 million M\u2609)<\/option>\n        <\/select>\n        <div class=\"eco-tool__hint\">Presets use approximate values.<\/div>\n      <\/div>\n\n      <!-- Mass -->\n      <div class=\"eco-tool__field\">\n        <label class=\"eco-tool__label\" for=\"eco-bh-mass-55a1c\">\n          Mass<br>value\n        <\/label>\n        <input class=\"eco-tool__input\" id=\"eco-bh-mass-55a1c\" type=\"number\" min=\"0\" step=\"any\" value=\"1\" inputmode=\"decimal\" \/>\n        <div class=\"eco-tool__hint\">Enter a mass and choose a unit.<\/div>\n      <\/div>\n\n      <!-- Unit -->\n      <div class=\"eco-tool__field\">\n        <label class=\"eco-tool__label\" for=\"eco-bh-unit-55a1c\">\n          Mass<br>unit\n        <\/label>\n        <select class=\"eco-tool__input\" id=\"eco-bh-unit-55a1c\">\n          <option value=\"msun\" selected>Solar masses (M\u2609)<\/option>\n          <option value=\"mearth\">Earth masses (M\u2295)<\/option>\n          <option value=\"kg\">Kilograms (kg)<\/option>\n        <\/select>\n        <div class=\"eco-tool__hint\">We convert everything to kg internally.<\/div>\n      <\/div>\n    <\/div>\n\n    <div class=\"eco-tool__actions\">\n      <button type=\"button\" class=\"wp-element-button eco-tool__btn\" id=\"eco-bh-calc-55a1c\">Calculate<\/button>\n      <button type=\"button\" class=\"wp-element-button eco-tool__btn eco-tool__btn--ghost\" id=\"eco-bh-reset-55a1c\">Reset<\/button>\n      <div class=\"eco-tool__error\" id=\"eco-bh-error-55a1c\" aria-live=\"polite\"><\/div>\n    <\/div>\n  <\/form>\n\n  <div class=\"eco-tool__result\" id=\"eco-bh-result-55a1c\" hidden>\n    <h3 class=\"eco-tool__subtitle\">Schwarzschild radius<\/h3>\n\n    <div class=\"eco-tool__cards\">\n      <div class=\"eco-tool__card\">\n        <div class=\"eco-tool__metric-label\">Event horizon radius<\/div>\n        <div class=\"eco-tool__metric-value\" id=\"eco-bh-km-55a1c\">\u2014<\/div>\n        <div class=\"eco-tool__metric-sub\" id=\"eco-bh-m-55a1c\">\u2014<\/div>\n      <\/div>\n\n      <div class=\"eco-tool__card\">\n        <div class=\"eco-tool__metric-label\">Diameter<\/div>\n        <div class=\"eco-tool__metric-value\" id=\"eco-bh-dia-55a1c\">\u2014<\/div>\n        <div class=\"eco-tool__metric-sub eco-tool__muted\">Twice the radius<\/div>\n      <\/div>\n    <\/div>\n\n    <div class=\"eco-tool__card eco-tool__card--wide\">\n      <div class=\"eco-tool__metric-label\">Interpretation<\/div>\n      <div class=\"eco-tool__metric-sub\" id=\"eco-bh-note-55a1c\"><\/div>\n    <\/div>\n\n    <p class=\"eco-tool__note\">\n      This is the ideal Schwarzschild radius (non-rotating, uncharged black hole). Real black holes can rotate (Kerr).\n    <\/p>\n  <\/div>\n\n  <details class=\"eco-tool__details\">\n    <summary class=\"eco-tool__summary\">How we calculate<\/summary>\n    <div class=\"eco-tool__details-body\">\n      <p class=\"eco-tool__text\">\n        r<sub>s<\/sub> = 2GM \/ c\u00b2, where G is the gravitational constant and c is the speed of light.\n      <\/p>\n    <\/div>\n  <\/details>\n<\/div>\n\n<style>\n.eco-tool{border:1px solid rgba(0,0,0,.12);border-radius:12px;padding:16px}\n.eco-tool__grid3{display:grid;grid-template-columns:1fr;gap:16px}\n@media (min-width:860px){.eco-tool__grid3{grid-template-columns:1fr 1fr 1fr}}\n.eco-tool__field{display:flex;flex-direction:column;gap:6px}\n.eco-tool__label{font-weight:600}\n.eco-tool__input{height:44px;padding:0 12px;border:1px solid rgba(0,0,0,.2);border-radius:10px;background:#fff;font:inherit;box-sizing:border-box}\n.eco-tool select.eco-tool__input{appearance:none;padding-right:40px}\n.eco-tool__hint{font-size:.92em;opacity:.78;min-height:38px}\n\n.eco-tool__actions{display:flex;gap:10px;margin-top:16px;align-items:center;flex-wrap:wrap}\n.eco-tool__btn{padding:10px 22px}\n.eco-tool__btn--ghost{background:transparent!important;border:1px solid rgba(0,0,0,.2)!important}\n.eco-tool__btn--ghost:hover,.eco-tool__btn--ghost:focus{background:rgba(0,0,0,.06)!important;border-color:rgba(0,0,0,.35)!important}\n.eco-tool__error{font-weight:600;min-height:1.2em;flex:1 1 240px}\n\n.eco-tool__result{margin-top:16px}\n.eco-tool__subtitle{margin:0 0 10px}\n.eco-tool__cards{display:grid;gap:10px;grid-template-columns:1fr}\n@media (min-width:860px){.eco-tool__cards{grid-template-columns:1fr 1fr}}\n.eco-tool__card{border:1px solid rgba(0,0,0,.12);border-radius:12px;padding:12px}\n.eco-tool__card--wide{margin-top:10px}\n.eco-tool__metric-label{opacity:.85;font-weight:600}\n.eco-tool__metric-value{font-size:1.6em;font-weight:800;margin-top:6px;line-height:1.1}\n.eco-tool__metric-sub{opacity:.85;margin-top:6px}\n.eco-tool__muted{opacity:.8}\n.eco-tool__note{margin-top:10px;opacity:.9}\n.eco-tool__details{margin-top:14px}\n.eco-tool__summary{cursor:pointer;font-weight:700}\n.eco-tool__details-body{margin-top:10px}\n<\/style>\n\n<script>\n(function(){\n  const S=\"55a1c\";\n  const el=(id)=>document.getElementById(id+\"-\"+S);\n\n  const presetEl=el(\"eco-bh-preset\");\n  const massEl=el(\"eco-bh-mass\");\n  const unitEl=el(\"eco-bh-unit\");\n\n  const calcBtn=el(\"eco-bh-calc\");\n  const resetBtn=el(\"eco-bh-reset\");\n  const errEl=el(\"eco-bh-error\");\n\n  const resEl=el(\"eco-bh-result\");\n  const kmEl=el(\"eco-bh-km\");\n  const mEl=el(\"eco-bh-m\");\n  const diaEl=el(\"eco-bh-dia\");\n  const noteEl=el(\"eco-bh-note\");\n\n  \/\/ Constants\n  const G = 6.67430e-11;         \/\/ m^3 kg^-1 s^-2\n  const C = 299792458;           \/\/ m\/s\n  const MSUN = 1.98847e30;       \/\/ kg\n  const MEARTH = 5.9722e24;      \/\/ kg\n\n  const PRESETS = {\n    custom: null,\n    earth: { mass: 1, unit: \"mearth\", label: \"Earth mass (1 M\u2295)\" },\n    sun:   { mass: 1, unit: \"msun\",   label: \"Sun mass (1 M\u2609)\" },\n    sgrA:  { mass: 4.0e6, unit: \"msun\", label: \"Sagittarius A* (~4.0 million M\u2609)\" }\n  };\n\n  function setError(msg){ errEl.textContent = msg || \"\"; }\n  function fmt(n,d){ return Number(n).toLocaleString(undefined,{maximumFractionDigits:d}); }\n\n  function toKg(val, unit){\n    if(unit === \"kg\") return val;\n    if(unit === \"msun\") return val * MSUN;\n    if(unit === \"mearth\") return val * MEARTH;\n    return val;\n  }\n\n  function applyPreset(){\n    const p = presetEl.value;\n    if(p !== \"custom\" && PRESETS[p]){\n      massEl.value = PRESETS[p].mass;\n      unitEl.value = PRESETS[p].unit;\n    }\n  }\n\n  function niceSize(diameterKm){\n    if (diameterKm < 1) return \"smaller than a city\";\n    if (diameterKm < 100) return \"about the size of a region\";\n    if (diameterKm < 13000) return \"comparable to a planet-scale size\";\n    return \"enormous \u2014 larger than many planetary distances\";\n  }\n\n  function calculate(){\n    setError(\"\");\n\n    const v = Number(massEl.value);\n    const unit = unitEl.value;\n\n    if(!Number.isFinite(v) || v <= 0){\n      setError(\"Please enter a valid mass value.\");\n      resEl.hidden = true;\n      return;\n    }\n\n    const M = toKg(v, unit);\n\n    \/\/ Schwarzschild radius: rs = 2GM\/c^2\n    const rs_m = (2 * G * M) \/ (C * C);      \/\/ meters\n    const rs_km = rs_m \/ 1000;\n    const dia_km = 2 * rs_km;\n\n    kmEl.textContent = `${fmt(rs_km,3)} km`;\n    mEl.textContent = `${fmt(rs_m,0)} m`;\n    diaEl.textContent = `${fmt(dia_km,3)} km`;\n\n    noteEl.textContent = `If you compressed that mass into a sphere smaller than ~${fmt(dia_km,3)} km across, it would form an event horizon (simplified Schwarzschild case). It\u2019s ${niceSize(dia_km)}.`;\n\n    resEl.hidden = false;\n  }\n\n  function reset(){\n    presetEl.value = \"sun\";\n    applyPreset();\n    setError(\"\");\n    resEl.hidden = true;\n  }\n\n  \/\/ init\n  presetEl.addEventListener(\"change\", applyPreset);\n  calcBtn.addEventListener(\"click\", calculate);\n  resetBtn.addEventListener(\"click\", reset);\n  presetEl.value = \"sun\";\n  applyPreset();\n})();\n<\/script>\n\n","protected":false},"excerpt":{"rendered":"<p>Black Hole Radius Calculator Calculate the Schwarzschild radius (event horizon) for a non-rotating black hole from its mass. Presetmass CustomEarth mass (1 M\u2295)Sun mass (1 M\u2609)Sagittarius A* (~4.0 million M\u2609)&hellip;<\/p>\n","protected":false},"author":2,"featured_media":0,"parent":2295,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_sitemap_exclude":false,"_sitemap_priority":"","_sitemap_frequency":"","footnotes":""},"_links":{"self":[{"href":"https:\/\/science-x.net\/index.php?rest_route=\/wp\/v2\/pages\/2387"}],"collection":[{"href":"https:\/\/science-x.net\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/science-x.net\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/science-x.net\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/science-x.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2387"}],"version-history":[{"count":1,"href":"https:\/\/science-x.net\/index.php?rest_route=\/wp\/v2\/pages\/2387\/revisions"}],"predecessor-version":[{"id":2388,"href":"https:\/\/science-x.net\/index.php?rest_route=\/wp\/v2\/pages\/2387\/revisions\/2388"}],"up":[{"embeddable":true,"href":"https:\/\/science-x.net\/index.php?rest_route=\/wp\/v2\/pages\/2295"}],"wp:attachment":[{"href":"https:\/\/science-x.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2387"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}