diff --git a/app.js b/app.js
index 2c60ebe..eea282d 100644
--- a/app.js
+++ b/app.js
@@ -20,6 +20,124 @@
   if (signupEl) signupEl.textContent = text;
 })();
 
+// ── Benefit Calculator ───────────────────────────────────
+(function initCalculator() {
+  const overlay   = document.getElementById('calcOverlay');
+  const openBtn   = document.getElementById('openCalc');
+  const closeBtn  = document.getElementById('calcClose');
+  const submitBtn = document.getElementById('calcSubmit');
+  const recalcBtn = document.getElementById('calcRecalc');
+  const calcForm  = document.getElementById('calcForm');
+  const calcRes   = document.getElementById('calcResults');
+  const calcErr   = document.getElementById('calcError');
+  const ctaBtn    = document.getElementById('calcCTABtn');
+
+  if (!overlay) return;
+
+  function open()  { overlay.classList.add('open'); document.body.style.overflow = 'hidden'; }
+  function close() { overlay.classList.remove('open'); document.body.style.overflow = ''; }
+
+  openBtn?.addEventListener('click', open);
+  closeBtn?.addEventListener('click', close);
+  overlay.addEventListener('click', e => { if (e.target === overlay) close(); });
+  document.addEventListener('keydown', e => { if (e.key === 'Escape') close(); });
+
+  recalcBtn?.addEventListener('click', () => {
+    calcRes.classList.add('hidden');
+    calcForm.classList.remove('hidden');
+  });
+
+  // Close modal and scroll to signup when CTA clicked
+  ctaBtn?.addEventListener('click', () => {
+    close();
+  });
+
+  submitBtn?.addEventListener('click', () => {
+    const homesites    = parseFloat(document.getElementById('calcHomesites').value)    || 0;
+    const propertyType = document.getElementById('calcPropertyType').value;
+    const annualIncome = parseFloat(document.getElementById('calcAnnualIncome').value) || 0;
+    const paymentFreq  = document.getElementById('calcPaymentFreq').value;
+    const reserveFunds = parseFloat(document.getElementById('calcReserveFunds').value) || 0;
+    const interest2025 = parseFloat(document.getElementById('calcInterest2025').value) || 0;
+
+    if (!homesites || !annualIncome) {
+      calcErr.classList.remove('hidden');
+      return;
+    }
+    calcErr.classList.add('hidden');
+
+    // ── Conservative investment assumptions ──
+    // Operating cash: depending on payment frequency, portion investable in high-yield savings
+    const opMultiplier  = { monthly: 0.10, quarterly: 0.20, annually: 0.35 }[paymentFreq] || 0.10;
+    const opRate        = 0.040;   // 4.0% money market / HYSA
+    const resRatio      = 0.65;    // 65% of reserves investable (keep 35% liquid)
+    const resRate       = 0.0425;  // 4.25% CD ladder / short-term treasuries
+
+    const investableOp  = annualIncome * opMultiplier;
+    const investableRes = reserveFunds * resRatio;
+    const opInterest    = Math.round(investableOp  * opRate);
+    const resInterest   = Math.round(investableRes * resRate);
+    const totalPotential = opInterest + resInterest;
+    const increase       = totalPotential - interest2025;
+    const pctIncrease    = interest2025 > 0
+      ? Math.round((increase / interest2025) * 100)
+      : (totalPotential > 0 ? 100 : 0);
+
+    // ── Populate results ──
+    const fmt = n => '$' + Math.round(n).toLocaleString();
+
+    document.getElementById('resultAmount').textContent   = fmt(totalPotential);
+    document.getElementById('resultCurrent').textContent  = fmt(interest2025);
+    document.getElementById('resultOperating').textContent = fmt(opInterest);
+    document.getElementById('resultReserve').textContent   = fmt(resInterest);
+
+    const badge = document.getElementById('resultBadge');
+    if (increase > 0) {
+      badge.textContent = `+${fmt(increase)} · +${pctIncrease}%`;
+      badge.style.display = 'inline-block';
+    } else {
+      badge.style.display = 'none';
+    }
+
+    // ── AI-style suggestion text ──
+    const typeLabels = { sfh:'single-family home', townhomes:'townhome', condos:'condo', mixed:'mixed-use', '':'' };
+    const typeLabel  = typeLabels[propertyType] || '';
+    const freqLabel  = { monthly:'monthly', quarterly:'quarterly', annually:'annual' }[paymentFreq];
+    const communityDesc = [homesites && `${homesites}-unit`, typeLabel, 'community'].filter(Boolean).join(' ');
+
+    let ai = `Based on your ${communityDesc} collecting ${fmt(annualIncome)} in ${freqLabel} dues`;
+    if (reserveFunds > 0) ai += ` and ${fmt(reserveFunds)} in reserve funds`;
+    ai += `, a conservative investment strategy could generate approximately ${fmt(totalPotential)} in annual interest income. `;
+    if (resInterest > 0) ai += `Deploying ${fmt(investableRes)} of your reserve funds into a short-term CD ladder at ~4.25% yields ${fmt(resInterest)} annually. `;
+    if (opInterest > 0)  ai += `Keeping a ${fmt(investableOp)} operating cash buffer in a high-yield money market at ~4.0% adds another ${fmt(opInterest)}. `;
+    if (interest2025 > 0 && increase > 0) {
+      ai += `That's a ${fmt(increase)} improvement (+${pctIncrease}%) over your 2025 interest income of ${fmt(interest2025)} — with no additional risk.`;
+    } else if (interest2025 === 0) {
+      ai += `This would represent entirely new interest income for your community at no additional risk.`;
+    }
+
+    document.getElementById('calcAiText').textContent = ai;
+
+    // ── Animate the main number ──
+    animateValue(document.getElementById('resultAmount'), 0, totalPotential);
+
+    calcForm.classList.add('hidden');
+    calcRes.classList.remove('hidden');
+  });
+
+  function animateValue(el, from, to) {
+    const duration = 900;
+    const start = performance.now();
+    function step(now) {
+      const progress = Math.min((now - start) / duration, 1);
+      const ease = 1 - Math.pow(1 - progress, 3);
+      el.textContent = '$' + Math.round(from + (to - from) * ease).toLocaleString();
+      if (progress < 1) requestAnimationFrame(step);
+    }
+    requestAnimationFrame(step);
+  }
+})();
+
 // ── Screenshot Carousel ──────────────────────────────────
 (function initCarousel() {
   const carousel = document.getElementById('screenshotCarousel');
diff --git a/index.html b/index.html
index 4375105..c23efcb 100644
--- a/index.html
+++ b/index.html
@@ -63,6 +63,7 @@
       </p>
       <div class="hero-actions">
         <a href="#preview-signup" class="btn btn-primary btn-lg">Join the Preview List</a>
+        <button class="btn btn-calc btn-lg" id="openCalc">✦ Calculate Your Interest Income Potential</button>
         <a href="#features" class="btn btn-ghost btn-lg">See What's Inside ↓</a>
       </div>
       <div class="hero-trust">
@@ -428,6 +429,106 @@
     </div>
   </footer>
 
+  <!-- ── BENEFIT CALCULATOR MODAL ─────────────────────── -->
+  <div class="calc-overlay" id="calcOverlay" aria-modal="true" role="dialog">
+    <div class="calc-modal">
+      <button class="calc-close" id="calcClose" aria-label="Close calculator">×</button>
+
+      <div class="calc-header">
+        <div class="section-label">ROI Calculator</div>
+        <h2>See What LedgerIQ Could Earn Your Community</h2>
+        <p>Answer a few quick questions for a personalized, conservative interest income estimate.</p>
+      </div>
+
+      <!-- INPUTS -->
+      <div id="calcForm">
+        <div class="calc-grid">
+          <div class="calc-field">
+            <label for="calcHomesites">Number of Homesites</label>
+            <input type="number" id="calcHomesites" placeholder="e.g. 150" min="1" />
+          </div>
+          <div class="calc-field">
+            <label for="calcPropertyType">Property Type</label>
+            <select id="calcPropertyType">
+              <option value="">Select type...</option>
+              <option value="sfh">Single Family Homes</option>
+              <option value="townhomes">Townhomes</option>
+              <option value="condos">Condos</option>
+              <option value="mixed">Mixed Use</option>
+            </select>
+          </div>
+          <div class="calc-field">
+            <label for="calcAnnualIncome">Annual Dues Income</label>
+            <div class="input-prefix-wrap">
+              <span class="input-prefix">$</span>
+              <input type="number" id="calcAnnualIncome" placeholder="e.g. 250,000" min="0" />
+            </div>
+          </div>
+          <div class="calc-field">
+            <label for="calcPaymentFreq">Dues Payment Frequency</label>
+            <select id="calcPaymentFreq">
+              <option value="monthly">Monthly</option>
+              <option value="quarterly">Quarterly</option>
+              <option value="annually">Annually</option>
+            </select>
+          </div>
+          <div class="calc-field">
+            <label for="calcReserveFunds">Current Reserve Fund Balance</label>
+            <div class="input-prefix-wrap">
+              <span class="input-prefix">$</span>
+              <input type="number" id="calcReserveFunds" placeholder="e.g. 500,000" min="0" />
+            </div>
+          </div>
+          <div class="calc-field">
+            <label for="calcInterest2025">Interest Income Earned in 2025</label>
+            <div class="input-prefix-wrap">
+              <span class="input-prefix">$</span>
+              <input type="number" id="calcInterest2025" placeholder="e.g. 4,500" min="0" />
+            </div>
+          </div>
+        </div>
+        <p class="calc-error hidden" id="calcError">Please fill in homesites and annual dues income to continue.</p>
+        <button class="btn btn-primary btn-lg calc-submit-btn" id="calcSubmit">Calculate My Potential →</button>
+        <p class="calc-fine">Conservative estimates for illustrative purposes only. Not financial advice.</p>
+      </div>
+
+      <!-- RESULTS -->
+      <div id="calcResults" class="hidden">
+        <div class="result-highlight">
+          <div class="result-label">Estimated Annual Interest Income Potential</div>
+          <div class="result-amount" id="resultAmount">$0</div>
+          <div class="result-comparison">
+            <span>vs. your 2025 earnings: <strong id="resultCurrent">$0</strong></span>
+            <span class="result-badge" id="resultBadge"></span>
+          </div>
+        </div>
+
+        <div class="result-breakdown">
+          <div class="result-row">
+            <span>Operating fund cash management</span>
+            <span class="result-row-val" id="resultOperating">$0</span>
+          </div>
+          <div class="result-row">
+            <span>Reserve fund investment income</span>
+            <span class="result-row-val" id="resultReserve">$0</span>
+          </div>
+        </div>
+
+        <div class="calc-ai-bubble">
+          <span class="ai-label">✦ LedgerIQ AI Estimate</span>
+          <p id="calcAiText"></p>
+        </div>
+
+        <div class="calc-cta">
+          <p>Ready to put these gains to work for your community?</p>
+          <a href="#preview-signup" class="btn btn-primary btn-lg calc-cta-btn" id="calcCTABtn">Get Early Access — Reserve My Spot →</a>
+          <button class="btn btn-ghost calc-recalc" id="calcRecalc">← Recalculate</button>
+        </div>
+      </div>
+
+    </div>
+  </div>
+
   <script src="app.js"></script>
 </body>
 </html>
diff --git a/styles.css b/styles.css
index 08132ee..a243222 100644
--- a/styles.css
+++ b/styles.css
@@ -623,6 +623,223 @@ body {
   color: var(--gray-700);
 }
 
+/* ---- Calculator CTA button ---- */
+.btn-calc {
+  background: linear-gradient(135deg, rgba(79,70,229,0.25), rgba(14,165,233,0.2));
+  border: 1.5px solid rgba(99,102,241,0.6);
+  color: #c7d2fe;
+  position: relative;
+  overflow: hidden;
+}
+.btn-calc::before {
+  content: '';
+  position: absolute;
+  inset: 0;
+  background: linear-gradient(135deg, rgba(79,70,229,0.4), rgba(14,165,233,0.3));
+  opacity: 0;
+  transition: opacity 0.2s;
+}
+.btn-calc:hover { color: #fff; border-color: rgba(99,102,241,0.9); transform: translateY(-1px); box-shadow: 0 8px 28px rgba(79,70,229,0.3); }
+.btn-calc:hover::before { opacity: 1; }
+.btn-calc span, .btn-calc { position: relative; z-index: 1; }
+
+/* ---- Calculator Modal ---- */
+.calc-overlay {
+  position: fixed;
+  inset: 0;
+  background: rgba(0,0,0,0.75);
+  backdrop-filter: blur(6px);
+  z-index: 1000;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  padding: 24px;
+  opacity: 0;
+  pointer-events: none;
+  transition: opacity 0.25s ease;
+}
+.calc-overlay.open {
+  opacity: 1;
+  pointer-events: all;
+}
+.calc-modal {
+  background: var(--gray-800);
+  border: 1px solid rgba(99,102,241,0.35);
+  border-radius: var(--radius-lg);
+  padding: 44px 48px;
+  max-width: 700px;
+  width: 100%;
+  max-height: 90vh;
+  overflow-y: auto;
+  position: relative;
+  box-shadow: 0 0 80px rgba(79,70,229,0.25), var(--shadow-lg);
+  transform: translateY(16px);
+  transition: transform 0.25s ease;
+}
+.calc-overlay.open .calc-modal { transform: translateY(0); }
+.calc-close {
+  position: absolute;
+  top: 16px; right: 20px;
+  background: none;
+  border: none;
+  color: var(--gray-500);
+  font-size: 26px;
+  cursor: pointer;
+  line-height: 1;
+  padding: 4px 8px;
+  border-radius: 6px;
+  transition: color 0.15s, background 0.15s;
+}
+.calc-close:hover { color: #fff; background: rgba(255,255,255,0.08); }
+.calc-header { margin-bottom: 28px; }
+.calc-header h2 { font-size: 26px; font-weight: 800; color: #fff; letter-spacing: -0.02em; margin-bottom: 8px; }
+.calc-header p { font-size: 15px; color: var(--gray-400); }
+.calc-grid {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: 16px;
+  margin-bottom: 8px;
+}
+.calc-field { display: flex; flex-direction: column; gap: 6px; }
+.calc-field label { font-size: 13px; font-weight: 600; color: var(--gray-400); }
+.calc-field input,
+.calc-field select {
+  background: var(--gray-900);
+  border: 1px solid rgba(255,255,255,0.1);
+  border-radius: 8px;
+  padding: 11px 14px;
+  color: var(--gray-100);
+  font-size: 15px;
+  font-family: inherit;
+  width: 100%;
+  outline: none;
+  transition: border-color 0.15s;
+  -webkit-appearance: none;
+}
+.calc-field input:focus,
+.calc-field select:focus { border-color: var(--blue); box-shadow: 0 0 0 3px rgba(37,99,235,0.2); }
+.calc-field input::placeholder { color: var(--gray-700); }
+.calc-field select {
+  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1 1l5 5 5-5' stroke='%2394a3b8' stroke-width='1.5' fill='none' stroke-linecap='round'/%3E%3C/svg%3E");
+  background-repeat: no-repeat;
+  background-position: right 14px center;
+  padding-right: 36px;
+}
+.calc-field select option { background: var(--gray-800); color: var(--gray-100); }
+.input-prefix-wrap { position: relative; }
+.input-prefix {
+  position: absolute;
+  left: 13px;
+  top: 50%;
+  transform: translateY(-50%);
+  color: var(--gray-600);
+  font-size: 15px;
+  font-weight: 600;
+  pointer-events: none;
+}
+.input-prefix-wrap input { padding-left: 28px; }
+.calc-error {
+  color: #f87171;
+  font-size: 13px;
+  margin: 8px 0;
+  font-weight: 500;
+}
+.calc-submit-btn { width: 100%; justify-content: center; margin-top: 16px; }
+.calc-fine {
+  font-size: 11px;
+  color: var(--gray-700);
+  text-align: center;
+  margin-top: 10px;
+  line-height: 1.5;
+}
+
+/* ── Results ── */
+.result-highlight {
+  background: linear-gradient(135deg, rgba(79,70,229,0.18), rgba(14,165,233,0.12));
+  border: 1px solid rgba(79,70,229,0.4);
+  border-radius: var(--radius);
+  padding: 28px;
+  text-align: center;
+  margin-bottom: 20px;
+}
+.result-label {
+  font-size: 12px;
+  text-transform: uppercase;
+  letter-spacing: 0.08em;
+  color: var(--gray-500);
+  font-weight: 700;
+  margin-bottom: 10px;
+}
+.result-amount {
+  font-size: 52px;
+  font-weight: 900;
+  letter-spacing: -0.03em;
+  color: var(--green);
+  line-height: 1.1;
+  margin-bottom: 12px;
+}
+.result-comparison {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: 12px;
+  flex-wrap: wrap;
+  font-size: 14px;
+  color: var(--gray-400);
+}
+.result-badge {
+  background: rgba(34,197,94,0.15);
+  border: 1px solid rgba(34,197,94,0.35);
+  color: var(--green);
+  padding: 3px 12px;
+  border-radius: 99px;
+  font-size: 13px;
+  font-weight: 700;
+  white-space: nowrap;
+}
+.result-breakdown {
+  background: rgba(255,255,255,0.03);
+  border: 1px solid rgba(255,255,255,0.07);
+  border-radius: var(--radius);
+  padding: 16px 20px;
+  margin-bottom: 20px;
+  display: flex;
+  flex-direction: column;
+  gap: 10px;
+}
+.result-row {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  font-size: 14px;
+  color: var(--gray-400);
+}
+.result-row-val { font-weight: 700; color: var(--gray-200); }
+.calc-ai-bubble {
+  background: rgba(79,70,229,0.12);
+  border: 1px solid rgba(79,70,229,0.3);
+  border-radius: var(--radius);
+  padding: 18px 20px;
+  margin-bottom: 24px;
+  font-size: 14px;
+  color: var(--gray-200);
+  line-height: 1.65;
+}
+.calc-ai-bubble .ai-label {
+  display: block;
+  font-size: 11px;
+  font-weight: 700;
+  color: #a5b4fc;
+  text-transform: uppercase;
+  letter-spacing: 0.06em;
+  margin-bottom: 8px;
+}
+.calc-cta { text-align: center; }
+.calc-cta > p { color: var(--gray-400); font-size: 15px; margin-bottom: 16px; }
+.calc-cta-btn { width: 100%; justify-content: center; margin-bottom: 12px; }
+.calc-recalc { font-size: 14px; color: var(--gray-500); }
+.calc-recalc:hover { color: var(--gray-200); }
+
 /* ---- Screenshot Carousel ---- */
 .screenshot-carousel {
   width: 100%;