diff --git a/src/InterOp/RunResult.php b/src/InterOp/RunResult.php
index 840f224..83f8e8c 100644
--- a/src/InterOp/RunResult.php
+++ b/src/InterOp/RunResult.php
@@ -10,10 +10,20 @@ class RunResult
 
     public SequencingQualityControl $sequencingQualityControl;
 
-    public function __construct(ClusterStatistic $clusterStatistic, SequencingQualityControl $sequencingQualityControl)
+    /**
+     * Share of flowcell wells occupied by a cluster, null on unpatterned flowcells.
+     *
+     * Patterned flowcells (NovaSeq X Plus, MiSeq i100) prescribe cluster locations,
+     * so occupancy replaces density as the measure of flowcell loading.
+     * Unpatterned flowcells report "nan".
+     */
+    public ?float $percentOccupied;
+
+    public function __construct(ClusterStatistic $clusterStatistic, SequencingQualityControl $sequencingQualityControl, ?float $percentOccupied)
     {
         $this->clusterStatistic = $clusterStatistic;
         $this->sequencingQualityControl = $sequencingQualityControl;
+        $this->percentOccupied = $percentOccupied;
     }
 
     /** @param array<string, string> $nonIndexedRow */
@@ -35,6 +45,10 @@ public static function fromLaneResults(LaneResult $read1, LaneResult $read2, arr
             $aggregated->sequencingQualityControl->error
         );
 
-        return new self($aggregated->clusterStatistic, $sequencingQualityControl);
+        return new self(
+            $aggregated->clusterStatistic,
+            $sequencingQualityControl,
+            SafeCast::tryFloat($nonIndexedRow['% Occupied'] ?? null)
+        );
     }
 }
diff --git a/tests/InterOp/MetaInfoTest.php b/tests/InterOp/MetaInfoTest.php
index 4b0074d..dca794e 100644
--- a/tests/InterOp/MetaInfoTest.php
+++ b/tests/InterOp/MetaInfoTest.php
@@ -51,6 +51,7 @@ public function testParseMiSeq(): void
         self::assertSame(83.2, $runQC->q30);
         self::assertSame(6.11, $runQC->aligned->value);
         self::assertEqualsWithDelta(0.065, $runQC->phasing, 0.001);
+        self::assertNull($metaInfo->interOpResult->resultsForRun->percentOccupied);
 
         self::assertSame('example-server/miseq_active\\230421_M02074_0859_000000000-KT6CY\\meta-info.json', $metaInfo->uncPath);
     }
@@ -91,6 +92,8 @@ public function testParseMiSeqI100(): void
         self::assertSame(3486, $metaInfo->interOpResult->resultsForRead2->intensityCycle);
         self::assertSame(1490000, $metaInfo->interOpResult->resultsForRead2->yield);
 
+        self::assertSame(74.22, $metaInfo->interOpResult->resultsForRun->percentOccupied);
+
         self::assertSame('example-server/miseq_active\\miSeqi100\\20260205_SH01038_0007_ASC2139476-SC3\\meta-info.json', $metaInfo->uncPath);
     }
 }