diff --git a/python/test/pyLink_TEST.py b/python/test/pyLink_TEST.py
index a31852ebb..41391f897 100644
--- a/python/test/pyLink_TEST.py
+++ b/python/test/pyLink_TEST.py
@@ -580,7 +580,7 @@ def test_resolveauto_inertialsWithMassAndMultipleCollisions(self):
         "  <model name='compound_model'>" + \
         "   <link name='compound_link'>" + \
         "     <inertial auto='True'>" + \
-        "       <mass>4.0</mass>" + \
+        "       <mass>12.0</mass>" + \
         "       <pose>1 1 1 2 2 2</pose>" + \
         "       <inertia>" + \
         "         <ixx>1</ixx>" + \
@@ -588,21 +588,78 @@ def test_resolveauto_inertialsWithMassAndMultipleCollisions(self):
         "         <izz>1</izz>" + \
         "       </inertia>" + \
         "     </inertial>" + \
+        "     <collision name='cube_collision'>" + \
+        "       <pose>0.0 0.0 0.5 0 0 0</pose>" + \
+        "      <density>4.0</density>" + \
+        "      <geometry>" + \
+        "        <box>" + \
+        "          <size>1 1 1</size>" + \
+        "        </box>" + \
+        "        </geometry>" + \
+        "      </collision>" + \
         "     <collision name='box_collision'>" + \
+        "       <pose>0.0 0.0 -1.0 0 0 0</pose>" + \
+        "       <density>1.0</density>" + \
+        "       <geometry>" + \
+        "         <box>" + \
+        "           <size>1 1 2</size>" + \
+        "         </box>" + \
+        "       </geometry>" + \
+        "    </collision>" + \
+        "  </link>" + \
+        " </model>" + \
+        "</sdf>"
+
+        root = Root()
+        sdfParserConfig = ParserConfig()
+        errors = root.load_sdf_string(sdf, sdfParserConfig)
+        self.assertEqual(errors, None)
+
+        model = root.model()
+        link = model.link_by_index(0)
+        errors = []
+        root.resolve_auto_inertials(errors, sdfParserConfig)
+        self.assertEqual(len(errors), 0)
+
+        self.assertEqual(12.0, link.inertial().mass_matrix().mass())
+        self.assertEqual(Pose3d.ZERO,
+                         link.inertial().pose())
+        self.assertEqual(Vector3d(9.0, 9.0, 2.0),
+            link.inertial().mass_matrix().diagonal_moments())
+
+    def test_resolveauto_inertialsWithMassAndDefaultDensity(self):
+        # The inertia matrix is specified but should be ignored.
+        # <mass> is speicifed - the auto computed inertial values should
+        # be scaled based on the desired mass.
+        # Density is not specified for the bottom collision - it should
+        # use the default value
+        sdf = "<?xml version=\"1.0\"?>" + \
+        "<sdf version=\"1.11\">" + \
+        "  <model name='compound_model'>" + \
+        "   <link name='compound_link'>" + \
+        "     <inertial auto='True'>" + \
+        "       <mass>12000.0</mass>" + \
+        "       <pose>1 1 1 2 2 2</pose>" + \
+        "       <inertia>" + \
+        "         <ixx>1</ixx>" + \
+        "         <iyy>1</iyy>" + \
+        "         <izz>1</izz>" + \
+        "       </inertia>" + \
+        "     </inertial>" + \
+        "     <collision name='cube_collision'>" + \
         "       <pose>0.0 0.0 0.5 0 0 0</pose>" + \
-        "      <density>2.0</density>" + \
+        "      <density>4000.0</density>" + \
         "      <geometry>" + \
         "        <box>" + \
         "          <size>1 1 1</size>" + \
         "        </box>" + \
         "        </geometry>" + \
         "      </collision>" + \
-        "     <collision name='box_collision2'>" + \
-        "       <pose>0.0 0.0 -0.5 0 0 0</pose>" + \
-        "       <density>4.0</density>" + \
+        "     <collision name='box_collision'>" + \
+        "       <pose>0.0 0.0 -1.0 0 0 0</pose>" + \
         "       <geometry>" + \
         "         <box>" + \
-        "           <size>1 1 1</size>" + \
+        "           <size>1 1 2</size>" + \
         "         </box>" + \
         "       </geometry>" + \
         "    </collision>" + \
@@ -621,10 +678,10 @@ def test_resolveauto_inertialsWithMassAndMultipleCollisions(self):
         root.resolve_auto_inertials(errors, sdfParserConfig)
         self.assertEqual(len(errors), 0)
 
-        self.assertEqual(4.0, link.inertial().mass_matrix().mass())
-        self.assertEqual(Pose3d(0, 0, -0.166667, 0, 0, 0),
+        self.assertEqual(12000.0, link.inertial().mass_matrix().mass())
+        self.assertEqual(Pose3d.ZERO,
                          link.inertial().pose())
-        self.assertEqual(Vector3d(1.55556, 1.55556, 0.666667),
+        self.assertEqual(Vector3d(9000.0, 9000.0, 2000.0),
             link.inertial().mass_matrix().diagonal_moments())
 
     def test_resolveauto_inertialsCalledWithAutoFalse(self):
diff --git a/src/Link_TEST.cc b/src/Link_TEST.cc
index 1ab1404dd..a2c346c2d 100644
--- a/src/Link_TEST.cc
+++ b/src/Link_TEST.cc
@@ -929,6 +929,115 @@ TEST(DOMLink, ResolveAutoInertialsWithMassAndMultipleCollisions)
     link->Inertial().MassMatrix().DiagonalMoments());
 }
 
+/////////////////////////////////////////////////
+TEST(DOMLink, ResolveAutoInertialsWithMassAndDefaultDensity)
+{
+  // A model with link inertial auto set to true.
+  // The inertia matrix is specified but should be ignored.
+  // <mass> is specified - the auto computed inertial values should
+  // be scaled based on the desired mass.
+  // The model contains two collisions with different sizes. Density
+  // is specified for the top collision but not the bottom collision.
+  // The model should have a lumped center of mass at the link origin.
+  std::string sdf = "<?xml version=\"1.0\"?>"
+  "<sdf version=\"1.11\">"
+  "  <model name='compound_model'>"
+  "   <link name='compound_link'>"
+  "     <inertial auto='true'>"
+  "       <mass>12000.0</mass>"
+  "       <pose>1 1 1 2 2 2</pose>"
+  "       <inertia>"
+  "         <ixx>1</ixx>"
+  "         <iyy>1</iyy>"
+  "         <izz>1</izz>"
+  "       </inertia>"
+  "     </inertial>"
+  "     <collision name='cube_collision'>"
+  "       <pose>0.0 0.0 0.5 0 0 0</pose>"
+  "       <density>4000</density>"
+  "       <geometry>"
+  "         <box>"
+  "           <size>1 1 1</size>"
+  "         </box>"
+  "       </geometry>"
+  "     </collision>"
+  "     <collision name='box_collision'>"
+  "       <pose>0.0 0.0 -1.0 0 0 0</pose>"
+  "       <geometry>"
+  "         <box>"
+  "           <size>1 1 2</size>"
+  "         </box>"
+  "       </geometry>"
+  "     </collision>"
+  "    </link>"
+  "  </model>"
+  "</sdf>";
+
+  sdf::Root root;
+  const sdf::ParserConfig sdfParserConfig;
+  sdf::Errors errors = root.LoadSdfString(sdf, sdfParserConfig);
+  EXPECT_TRUE(errors.empty());
+  EXPECT_NE(nullptr, root.Element());
+
+  const sdf::Model *model = root.Model();
+  const sdf::Link *link = model->LinkByIndex(0);
+  root.ResolveAutoInertials(errors, sdfParserConfig);
+  EXPECT_TRUE(errors.empty());
+
+  // Expect mass value from //inertial/mass
+  EXPECT_DOUBLE_EQ(12000.0, link->Inertial().MassMatrix().Mass());
+
+  // Inertial values based on density before scaling to match specified mass
+  //
+  // Collision geometries:
+  //
+  // --------- z = 1
+  // |       |
+  // |   c   | cube on top, side length 1.0, density 4000.0
+  // |       |
+  // |-------| z = 0
+  // |       |
+  // |       |
+  // |       |
+  // |   c   | box on bottom, size 1x1x2, default density 1000.0
+  // |       |
+  // |       |
+  // |       |
+  // --------- z = -2
+  //
+  //   Top cube: volume = 1.0, mass = 4000.0, center of mass z = 0.5
+  // Bottom box: volume = 2.0, mass = 2000.0, center of mass z = -1.0
+  //
+  // Total mass from density: 6000.0
+  // Lumped center of mass z = (4000.0 * 0.5 + 2000.0 * (-1.0)) / 6000.0 = 0.0
+  EXPECT_EQ(gz::math::Pose3d::Zero, link->Inertial().Pose());
+
+  // Moment of inertia at center of each shape
+  //   Top cube: Ixx = Iyy = Izz = 4000.0 / 12 * (1*1 + 1*1) = 8000/12
+  // Bottom box:       Ixx = Iyy = 2000.0 / 12 * (1*1 + 2*2) = 10000/12
+  //                         Izz = 2000.0 / 12 * (1*1 + 1*1) = 4000/12
+  //
+  // Lumped moment of inertia at lumped center of mass
+  // Ixx = sum(Ixx_i + mass_i * center_of_mass_z_i^2) for i in [top, bottom]
+  // Iyy = Ixx
+  // Izz = Izz_top + Izz_bottom
+  //
+  // Ixx = Iyy = (8000/12 + 4000.0 * 0.5 * 0.5) + (10000/12 + 2000.0
+  //                                              * (-1.0) * (-1.0))
+  //           = (8000/12 + 1000)               + (10000/12 + 2000.0)
+  //           = 20000/12                       + 34000/12
+  //           = 54000/12 = 9000/2 = 4500
+  //
+  // Izz = 8000/12 + 4000/12  = 1000.0
+
+  // Then scale the inertias according to the specified mass of 12000.0
+  // mass_ratio = 12000.0 / 6000.0 = 2.0
+  // Ixx = Iyy = mass_ratio * Ixx_unscaled = 2.0 * 4500.0 = 9000.0
+  //       Izz = mass_ratio * Izz_unscaled = 2.0 * 1000.0 = 2000.0
+  EXPECT_EQ(gz::math::Vector3d(9000.0, 9000.0, 2000.0),
+    link->Inertial().MassMatrix().DiagonalMoments());
+}
+
 /////////////////////////////////////////////////
 TEST(DOMLink, ResolveAutoInertialsCalledWithAutoFalse)
 {