diff --git a/css/styles.css b/css/styles.css
index 144330c..9aeeb7e 100644
--- a/css/styles.css
+++ b/css/styles.css
@@ -923,4 +923,107 @@ kbd {
     .warning-banner {
         border: 2px solid #f59e0b;
     }
+}
+
+/* --------------------------------------------------------------------------
+   Metric Tooltips
+   -------------------------------------------------------------------------- */
+.result-metric {
+    position: relative;
+    cursor: help;
+}
+
+.metric-tooltip {
+    visibility: hidden;
+    opacity: 0;
+    position: absolute;
+    bottom: 100%;
+    left: 50%;
+    transform: translateX(-50%);
+    margin-bottom: 12px;
+    padding: var(--space-md);
+    width: 280px;
+    background: var(--bg-primary);
+    border: 1px solid var(--border-color);
+    border-radius: var(--radius-md);
+    font-size: 0.8rem;
+    text-align: left;
+    z-index: 100;
+    box-shadow: var(--shadow-lg);
+    transition: opacity var(--transition-fast), visibility var(--transition-fast);
+}
+
+.metric-tooltip::after {
+    content: '';
+    position: absolute;
+    top: 100%;
+    left: 50%;
+    transform: translateX(-50%);
+    border: 8px solid transparent;
+    border-top-color: var(--border-color);
+}
+
+.result-metric:hover .metric-tooltip,
+.result-metric:focus .metric-tooltip,
+.result-metric:active .metric-tooltip {
+    visibility: visible;
+    opacity: 1;
+}
+
+.metric-tooltip strong {
+    display: block;
+    margin-bottom: var(--space-sm);
+    color: var(--accent);
+    font-size: 0.85rem;
+}
+
+.metric-tooltip p {
+    margin: 0 0 var(--space-sm);
+    color: var(--text-secondary);
+    line-height: 1.4;
+}
+
+.tooltip-scale {
+    display: flex;
+    flex-direction: column;
+    gap: 2px;
+    margin: var(--space-sm) 0;
+    padding: var(--space-sm);
+    background: var(--bg-tertiary);
+    border-radius: var(--radius-sm);
+    font-family: var(--font-mono);
+    font-size: 0.7rem;
+}
+
+.scale-good {
+    color: var(--success);
+}
+
+.scale-ok {
+    color: var(--warning);
+}
+
+.scale-bad {
+    color: var(--danger);
+}
+
+.tooltip-hint {
+    margin-top: var(--space-sm);
+    padding-top: var(--space-sm);
+    border-top: 1px solid var(--border-color);
+    font-style: italic;
+    color: var(--text-muted);
+}
+
+/* Mobile: tap to show tooltip */
+@media (max-width: 640px) {
+    .metric-tooltip {
+        width: 240px;
+        left: 0;
+        transform: translateX(0);
+    }
+
+    .metric-tooltip::after {
+        left: 20%;
+    }
 }
\ No newline at end of file
diff --git a/index.html b/index.html
index 0d0f601..b8e608c 100644
--- a/index.html
+++ b/index.html
@@ -199,21 +199,60 @@
 
                 <!-- Results Summary -->
                 <div class="results-summary" id="results-summary">
-                    <div class="result-metric">
+                    <div class="result-metric" tabindex="0" data-tooltip="match-score">
                         <span class="metric-value" id="result-score">-</span>
                         <span class="metric-label">Match Score</span>
+                        <div class="metric-tooltip">
+                            <strong>Match Score</strong>
+                            <p>Combined score from capacity and IR variance, weighted by your settings.</p>
+                            <div class="tooltip-scale">
+                                <span class="scale-good">&lt; 0.5 = Excellent</span>
+                                <span class="scale-ok">0.5 - 2.0 = Good</span>
+                                <span class="scale-bad">&gt; 2.0 = Poor</span>
+                            </div>
+                            <p class="tooltip-hint">Lower is better</p>
+                        </div>
                     </div>
-                    <div class="result-metric">
+                    <div class="result-metric" tabindex="0" data-tooltip="cap-cv">
                         <span class="metric-value" id="result-cap-variance">-</span>
                         <span class="metric-label">Capacity CV%</span>
+                        <div class="metric-tooltip">
+                            <strong>Capacity Coefficient of Variation</strong>
+                            <p>Measures how evenly matched the total capacity of each parallel group is. CV = (σ / μ) ×
+                                100%</p>
+                            <div class="tooltip-scale">
+                                <span class="scale-good">&lt; 1% = Excellent</span>
+                                <span class="scale-ok">1 - 3% = Acceptable</span>
+                                <span class="scale-bad">&gt; 3% = Poor balance</span>
+                            </div>
+                            <p class="tooltip-hint">Lower is better – ensures even discharge across series groups</p>
+                        </div>
                     </div>
-                    <div class="result-metric">
+                    <div class="result-metric" tabindex="0" data-tooltip="ir-cv">
                         <span class="metric-value" id="result-ir-variance">-</span>
                         <span class="metric-label">IR CV%</span>
+                        <div class="metric-tooltip">
+                            <strong>Internal Resistance Variation</strong>
+                            <p>Average variation of internal resistance within parallel groups. High mismatch causes
+                                uneven current distribution.</p>
+                            <div class="tooltip-scale">
+                                <span class="scale-good">&lt; 5% = Excellent</span>
+                                <span class="scale-ok">5 - 15% = Acceptable</span>
+                                <span class="scale-bad">&gt; 20% = Risk of 40% lifetime reduction</span>
+                            </div>
+                            <p class="tooltip-hint">Lower is better – critical for high-drain applications</p>
+                        </div>
                     </div>
-                    <div class="result-metric">
+                    <div class="result-metric" tabindex="0" data-tooltip="pack-cap">
                         <span class="metric-value" id="result-pack-capacity">-</span>
                         <span class="metric-label">Pack Capacity</span>
+                        <div class="metric-tooltip">
+                            <strong>Effective Pack Capacity</strong>
+                            <p>The usable capacity of your pack, limited by the smallest parallel group (weakest link).
+                            </p>
+                            <p>Formula: min(group capacities)</p>
+                            <p class="tooltip-hint">Higher is better – well-matched cells maximize this value</p>
+                        </div>
                     </div>
                 </div>
 
@@ -277,7 +316,7 @@
                 <a href="https://git.mosad.xyz/localhorst/LiXX_Cell_Pack_Matcher" target="_blank" rel="noopener">Git</a>
                 ·
                 Based on research by
-                <a href="https://doi.org/10.1016/j.jpowsour.2013.11.064" target="_blank" rel="noopener">Shi et al., 2013</a>
+                <a href="https://doi.org/10.1016/j.jpowsour.2013.11.064" target="_blank" rel="noopener">Wang et al., 2013</a>
             </p>
             <p class="disclaimer">
                 This tool is for educational purposes. Always consult professional guidance for battery pack assembly.