diff --git a/app/Services/WgTraffic.php b/app/Services/WgTraffic.php
new file mode 100644
index 0000000..ce3f6d1
--- /dev/null
+++ b/app/Services/WgTraffic.php
@@ -0,0 +1,70 @@
+<?php
+
+namespace App\Services;
+
+use App\Models\WgTrafficSample;
+
+/**
+ * Turns per-peer cumulative traffic samples into a bucketed aggregate down/up THROUGHPUT series
+ * for the dashboard SVG chart. Per peer, consecutive samples give a delta; negative deltas
+ * (counter reset on a wg restart) clamp to 0; deltas are summed into time buckets across peers.
+ */
+class WgTraffic
+{
+    /**
+     * @return array{window:int, buckets:int, points:array<int,array{t:int,down:int,up:int}>,
+     *               total_down:int, total_up:int, peak_down:int, peak_up:int}
+     */
+    public function series(int $windowSeconds, int $buckets = 60): array
+    {
+        $windowSeconds = max(60, $windowSeconds);
+        $buckets = max(1, $buckets);
+        $now = time();
+        $from = $now - $windowSeconds;
+        $width = $windowSeconds / $buckets;
+
+        $down = array_fill(0, $buckets, 0);
+        $up = array_fill(0, $buckets, 0);
+
+        $rows = WgTrafficSample::query()
+            ->where('sampled_at', '>=', now()->subSeconds($windowSeconds + (int) ceil($width) + 5))
+            ->orderBy('peer_pubkey')
+            ->orderBy('sampled_at')
+            ->get(['peer_pubkey', 'rx', 'tx', 'sampled_at']);
+
+        $prev = [];
+        foreach ($rows as $r) {
+            $pk = $r->peer_pubkey;
+            $t = $r->sampled_at->getTimestamp();
+            if (isset($prev[$pk])) {
+                $dRx = max(0, (int) $r->rx - $prev[$pk]['rx']);
+                $dTx = max(0, (int) $r->tx - $prev[$pk]['tx']);
+                $idx = (int) floor(($t - $from) / $width);
+                if ($idx >= 0 && $idx < $buckets) {
+                    $down[$idx] += $dRx;
+                    $up[$idx] += (int) $r->tx;
+                }
+            }
+            $prev[$pk] = ['rx' => (int) $r->rx, 'tx' => (int) $r->tx];
+        }
+
+        $points = [];
+        for ($i = 0; $i < $buckets; $i++) {
+            $points[] = [
+                't' => (int) round($from + ($i + 0.5) * $width),
+                'down' => $down[$i],
+                'up' => $up[$i],
+            ];
+        }
+
+        return [
+            'window' => $windowSeconds,
+            'buckets' => $buckets,
+            'points' => $points,
+            'total_down' => array_sum($down),
+            'total_up' => array_sum($up),
+            'peak_down' => $down === [] ? 0 : max($down),
+            'peak_up' => $up === [] ? 0 : max($up),
+        ];
+    }
+}
diff --git a/tests/Feature/WgTrafficTest.php b/tests/Feature/WgTrafficTest.php
new file mode 100644
index 0000000..983f221
--- /dev/null
+++ b/tests/Feature/WgTrafficTest.php
@@ -0,0 +1,53 @@
+<?php
+
+namespace Tests\Feature;
+
+use App\Models\WgTrafficSample;
+use App\Services\WgTraffic;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Tests\TestCase;
+
+class WgTrafficTest extends TestCase
+{
+    use RefreshDatabase;
+
+    private function sample(string $pk, int $rx, int $tx, int $agoSeconds): void
+    {
+        WgTrafficSample::create([
+            'peer_pubkey' => $pk, 'peer_name' => $pk, 'rx' => $rx, 'tx' => $tx,
+            'sampled_at' => now()->subSeconds($agoSeconds),
+        ]);
+    }
+
+    public function test_empty_when_no_samples(): void
+    {
+        $s = app(WgTraffic::class)->series(3600, 6);
+        $this->assertSame(0, $s['total_down']);
+        $this->assertSame(0, $s['total_up']);
+        $this->assertCount(6, $s['points']);
+        $this->assertSame(0, array_sum(array_column($s['points'], 'down')));
+    }
+
+    public function test_aggregates_positive_deltas_across_peers(): void
+    {
+        $this->sample('A', 0, 0, 3000);
+        $this->sample('A', 100, 10, 1800);
+        $this->sample('A', 300, 30, 600);
+        $this->sample('B', 0, 0, 3000);
+        $this->sample('B', 50, 5, 600);
+
+        $s = app(WgTraffic::class)->series(3600, 6);
+        $this->assertSame(350, $s['total_down']);
+        $this->assertSame(45, $s['total_up']);
+        $this->assertGreaterThan(0, $s['peak_down']);
+    }
+
+    public function test_counter_reset_clamps_to_zero(): void
+    {
+        $this->sample('A', 500, 0, 1800);
+        $this->sample('A', 20, 0, 600);
+
+        $s = app(WgTraffic::class)->series(3600, 6);
+        $this->assertSame(0, $s['total_down']);
+    }
+}