Backdoor Roth IRA Form 8606 & 2026 IRS RMD Table III Calculator

HTML

<div class="ec-card">
  <div class="ec-kicker">IRC § 408(d)(2) (FORM 8606 PRO-RATA) · IRS PUB. 590-B TABLE III (SECURE 2.0)</div>
  <h2>2026 Form 8606 Backdoor Roth Pro-Rata & RMD Calculator</h2>
  <label>Dec 31 Pre-Tax Rollover/SEP IRA Balance ($): <input id="pre" type="number" value="63000" step="5000"></label>
  <label>2026 Non-Deductible Roth Conversion ($): <input id="conv" type="number" value="7000" step="1000"></label>
  <button id="runBtn">Calculate Form 8606 Line 18 Taxable Amount</button>
  <div id="out"></div>
  <p class="ec-foot">Canonical Retirement Suite: <a href="https://eastcorpcapital.com/backdoor-roth-ira-step-by-step-guide-fidelity-vanguard-irs-form-8606-2026/" target="_blank" rel="noopener">Backdoor Roth IRA Form 8606 & 2026 IRS RMD Table III Calculator</a> · <a href="https://eastcorpcapital.com/rmd-calculator-2026-irs-uniform-lifetime-table-inherited-ira-10-year-rule/" target="_blank" rel="noopener">2026 IRS RMD Table III Calculator</a></p>
</div>

CSS

body{font-family:system-ui,-apple-system,sans-serif;background:#FAF8F5;padding:18px;color:#111827}.ec-card{max-width:650px;background:#fff;border:1px solid #D1D5DB;border-top:5px solid #B91C1C;padding:20px}.ec-kicker{font-family:monospace;font-size:11px;font-weight:700;color:#B91C1C}h2{margin:6px 0 12px;font-size:20px}label{display:block;font-weight:700;font-size:13px;margin-bottom:8px}input{padding:5px 9px;font-size:14px;width:150px;margin-left:8px}button{background:#B91C1C;color:#fff;border:none;padding:8px 14px;font-weight:700;cursor:pointer;margin:6px 0 14px}.res{background:#FEF2F2;border-left:4px solid #B91C1C;padding:12px;font-size:13.5px;line-height:1.6}.ec-foot{margin-top:12px;font-size:12px}a{color:#B91C1C;font-weight:700}

JavaScript

function calc(){
  const pre = parseFloat(document.getElementById('pre').value)||0;
  const conv = parseFloat(document.getElementById('conv').value)||7000;
  const total = pre + conv;
  const taxFreeRatio = total > 0 ? (conv / total) : 1;
  const taxable = conv * (1 - taxFreeRatio);
  document.getElementById('out').innerHTML = '<div class="res"><strong>Form 8606 Line 10 Tax-Free Ratio:</strong> ' + (taxFreeRatio*100).toFixed(2) + '%<br><strong>Form 8606 Line 18 Taxable Conversion Amount:</strong> <span style="color:#B91C1C;font-weight:700">$' + Math.round(taxable).toLocaleString() + '</span><br><strong>Reverse 401(k) Rollover Cure:</strong> Rolling $' + Math.round(pre).toLocaleString() + ' into your employer/Solo 401(k) by Dec 31 reduces taxable conversion to <strong>$0</strong>!</div>';
}
document.getElementById('runBtn').addEventListener('click', calc);
calc();