diff --git a/calc.js b/calc.js
index 013e084..d6c4fea 100644
--- a/calc.js
+++ b/calc.js
@@ -44,8 +44,12 @@ function run_simulation(p) {
   const renter_nw_arr = [];
   const cum_buy_arr = [];
   const cum_rent_arr = [];
+  const detail_arr = [];
   const labels = [];
 
+  // yearly accumulators (reset each year)
+  let yr_interest = 0, yr_principal = 0, yr_upkeep = 0;
+
   let breakeven_month = null;
 
   const invest_r_m = p.invest_return / 100 / 12;
@@ -65,7 +69,10 @@ function run_simulation(p) {
     // German context: no mortgage interest tax deduction for private buyers
     const total_buy_m = monthly_payment + prop_tax_m + maint_m + insurance_m;
 
-    cum_buy_cost += total_buy_m;
+    yr_interest   += interest_m;
+    yr_principal  += principal_m;
+    yr_upkeep     += prop_tax_m + maint_m + insurance_m;
+    cum_buy_cost  += total_buy_m;
 
     buyer_portfolio *= (1 + invest_r_m);
     const selling_costs = home_value * (p.closing_sell_pct / 100);
@@ -103,6 +110,14 @@ function run_simulation(p) {
       renter_nw_arr.push(Math.round(portfolio - tax_on_gains));
       cum_buy_arr.push(Math.round(cum_buy_cost));
       cum_rent_arr.push(Math.round(cum_rent_cost));
+      detail_arr.push({
+        house_value:     Math.round(home_value),
+        buyer_portfolio: Math.round(buyer_portfolio),
+        yr_interest:     Math.round(yr_interest),
+        yr_principal:    Math.round(yr_principal),
+        yr_upkeep:       Math.round(yr_upkeep),
+      });
+      yr_interest = 0; yr_principal = 0; yr_upkeep = 0;
     }
   }
 
@@ -116,6 +131,7 @@ function run_simulation(p) {
     renter_nw_arr,
     cum_buy_arr,
     cum_rent_arr,
+    detail_arr,
     monthly_payment: Math.round(monthly_payment),
     final_buyer_nw,
     final_renter_nw,
diff --git a/style.css b/style.css
index eeb90bd..1e7bd1f 100644
--- a/style.css
+++ b/style.css
@@ -409,6 +409,8 @@ th {
 
 tbody tr:hover { background: rgba(255,255,255,0.03); }
 
+td.has-tip { cursor: default; border-bottom-style: dashed; }
+
 tr.winner-row td { font-weight: 600; }
 
 /* ===== Footer ===== */
diff --git a/ui.js b/ui.js
index ffbe555..a66aa63 100644
--- a/ui.js
+++ b/ui.js
@@ -140,22 +140,91 @@ const update_chart = (chart, labels, data_buy, data_rent, breakeven_month, years
   chart.update('none');
 };
 
+// ===== Tooltip =====
+
+const tooltip_el = (() => {
+  const el = document.createElement('div');
+  el.id = 'tbl_tooltip';
+  el.style.cssText = `
+    position:fixed; z-index:1000; pointer-events:none; display:none;
+    background:rgba(13,17,23,0.96); border:1px solid rgba(255,255,255,0.12);
+    border-radius:10px; padding:0.7rem 1rem; font-size:0.8rem; line-height:1.8;
+    color:#e6edf3; white-space:nowrap; box-shadow:0 8px 32px rgba(0,0,0,0.5);
+  `;
+  document.body.appendChild(el);
+  return el;
+})();
+
+const show_tooltip = (e, html) => {
+  tooltip_el.innerHTML = html;
+  tooltip_el.style.display = 'block';
+  move_tooltip(e);
+};
+
+const move_tooltip = (e) => {
+  const pad = 14;
+  const tw = tooltip_el.offsetWidth;
+  const th = tooltip_el.offsetHeight;
+  let x = e.clientX + pad;
+  let y = e.clientY + pad;
+  if (x + tw > window.innerWidth  - pad) x = e.clientX - tw - pad;
+  if (y + th > window.innerHeight - pad) y = e.clientY - th - pad;
+  tooltip_el.style.left = x + 'px';
+  tooltip_el.style.top  = y + 'px';
+};
+
+const hide_tooltip = () => { tooltip_el.style.display = 'none'; };
+
+const tip_row = (label, value, color) =>
+  `<span style="color:${color || '#8b949e'}">${label}</span>  <b>${fmt_eur(value)}</b>`;
+
 // ===== Table =====
 
 const build_table = (result) => {
   const tbody = document.getElementById('table_body');
   tbody.innerHTML = '';
   for (let i = 0; i < result.labels.length; i++) {
+    const d = result.detail_arr[i];
     const tr = document.createElement('tr');
-    tr.innerHTML = `
-      <td>${result.labels[i]}</td>
-      <td>${fmt_eur(result.buyer_nw_arr[i])}</td>
-      <td>${fmt_eur(result.renter_nw_arr[i])}</td>
-      <td>${fmt_eur(result.cum_buy_arr[i])}</td>
-      <td>${fmt_eur(result.cum_rent_arr[i])}</td>
-    `;
+
+    const td_buy_nw = document.createElement('td');
+    td_buy_nw.textContent = fmt_eur(result.buyer_nw_arr[i]);
+    td_buy_nw.classList.add('has-tip');
+    td_buy_nw.addEventListener('mouseenter', (e) => show_tooltip(e, [
+      tip_row('Immobilienwert', d.house_value, '#f59e0b'),
+      tip_row('ETF-Portfolio',  d.buyer_portfolio, '#f59e0b'),
+    ].join('<br>')));
+
+    const td_rent_nw = document.createElement('td');
+    td_rent_nw.textContent = fmt_eur(result.renter_nw_arr[i]);
+    td_rent_nw.classList.add('has-tip');
+    td_rent_nw.addEventListener('mouseenter', (e) => show_tooltip(e, [
+      tip_row('ETF-Portfolio (nach Steuer)', result.renter_nw_arr[i], '#2dd4bf'),
+    ].join('<br>')));
+
+    const td_buy_cost = document.createElement('td');
+    td_buy_cost.textContent = fmt_eur(result.cum_buy_arr[i]);
+    td_buy_cost.classList.add('has-tip');
+    td_buy_cost.addEventListener('mouseenter', (e) => show_tooltip(e, [
+      `<span style="color:#8b949e;font-size:0.72rem;text-transform:uppercase;letter-spacing:.05em">dieses Jahr</span>`,
+      tip_row('Zinsen',    d.yr_interest,  '#f59e0b'),
+      tip_row('Tilgung',   d.yr_principal, '#f59e0b'),
+      tip_row('Nebenkosten', d.yr_upkeep,  '#f59e0b'),
+    ].join('<br>')));
+
+    const td_rent_cost = document.createElement('td');
+    td_rent_cost.textContent = fmt_eur(result.cum_rent_arr[i]);
+
+    tr.appendChild(document.createElement('td')).textContent = result.labels[i];
+    tr.appendChild(td_buy_nw);
+    tr.appendChild(td_rent_nw);
+    tr.appendChild(td_buy_cost);
+    tr.appendChild(td_rent_cost);
     tbody.appendChild(tr);
   }
+
+  tbody.addEventListener('mousemove',  move_tooltip);
+  tbody.addEventListener('mouseleave', hide_tooltip);
 };
 
 // ===== Result cards =====