diff --git a/ApplicationLibCode/ReservoirDataModel/RigMainGrid.cpp b/ApplicationLibCode/ReservoirDataModel/RigMainGrid.cpp
index 24c1d6c33d..71fab84de7 100644
--- a/ApplicationLibCode/ReservoirDataModel/RigMainGrid.cpp
+++ b/ApplicationLibCode/ReservoirDataModel/RigMainGrid.cpp
@@ -288,6 +288,8 @@ void RigMainGrid::computeCachedData( std::string* aabbTreeInfo )
         *aabbTreeInfo += "Cells per bounding box : " + std::to_string( cellsPerBoundingBox ) + "\n";
         *aabbTreeInfo += m_cellSearchTree->info();
     }
+
+    computeBoundingBox();
 }
 
 //--------------------------------------------------------------------------------------------------
@@ -433,6 +435,35 @@ bool RigMainGrid::hasFaultWithName( const QString& name ) const
     return false;
 }
 
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+void RigMainGrid::computeBoundingBox()
+{
+    m_boundingBox.reset();
+
+    const int numberOfThreads = RiaOpenMPTools::availableThreadCount();
+
+    std::vector<cvf::BoundingBox> threadBoundingBoxes( numberOfThreads );
+
+#pragma omp parallel
+    {
+        int myThread = RiaOpenMPTools::currentThreadIndex();
+
+        // NB! We are inside a parallel section, do not use "parallel for" here
+#pragma omp for
+        for ( long i = 0; i < static_cast<long>( m_nodes.size() ); i++ )
+        {
+            threadBoundingBoxes[myThread].add( m_nodes[i] );
+        }
+    }
+
+    for ( int i = 0; i < numberOfThreads; i++ )
+    {
+        m_boundingBox.add( threadBoundingBoxes[i] );
+    }
+}
+
 //--------------------------------------------------------------------------------------------------
 ///
 //--------------------------------------------------------------------------------------------------
@@ -943,13 +974,6 @@ void RigMainGrid::buildCellSearchTreeOptimized( size_t cellsPerBoundingBox )
 //--------------------------------------------------------------------------------------------------
 cvf::BoundingBox RigMainGrid::boundingBox() const
 {
-    if ( m_boundingBox.isValid() ) return m_boundingBox;
-
-    for ( const auto& node : m_nodes )
-    {
-        m_boundingBox.add( node );
-    }
-
     return m_boundingBox;
 }
 
diff --git a/ApplicationLibCode/ReservoirDataModel/RigMainGrid.h b/ApplicationLibCode/ReservoirDataModel/RigMainGrid.h
index dc0b682603..536a2a2d12 100644
--- a/ApplicationLibCode/ReservoirDataModel/RigMainGrid.h
+++ b/ApplicationLibCode/ReservoirDataModel/RigMainGrid.h
@@ -118,6 +118,7 @@ class RigMainGrid : public RigGridBase
     void buildCellSearchTree();
     void buildCellSearchTreeOptimized( size_t cellsPerBoundingBox );
     bool hasFaultWithName( const QString& name ) const;
+    void computeBoundingBox();
 
     static std::array<double, 6> defaultMapAxes();
 
@@ -133,7 +134,7 @@ class RigMainGrid : public RigGridBase
 
     cvf::Vec3d                     m_displayModelOffset;
     cvf::ref<cvf::BoundingBoxTree> m_cellSearchTree;
-    mutable cvf::BoundingBox       m_boundingBox;
+    cvf::BoundingBox               m_boundingBox;
 
     bool m_flipXAxis;
     bool m_flipYAxis;