diff --git a/grid_apps/utils.py b/grid_apps/utils.py
index 78e05fb..e3c2dae 100644
--- a/grid_apps/utils.py
+++ b/grid_apps/utils.py
@@ -586,7 +586,7 @@ def octree_2_treemesh(  # pylint: disable=too-many-locals
     ):
         return None
 
-    n_cell_dim, cell_sizes = [], []
+    cell_sizes = []
     for ax in "uvw":
         if (
             getattr(mesh, f"{ax}_cell_size") is None
@@ -594,24 +594,16 @@ def octree_2_treemesh(  # pylint: disable=too-many-locals
         ):
             raise ValueError(f"Cell size in {ax} direction is not defined.")
 
-        n_cell_dim.append(getattr(mesh, f"{ax}_count"))
         cell_sizes.append(
-            np.ones(getattr(mesh, f"{ax}_count")) * getattr(mesh, f"{ax}_cell_size")
+            np.full(getattr(mesh, f"{ax}_count"), getattr(mesh, f"{ax}_cell_size"))
         )
 
     if any(np.any(cell_size < 0) for cell_size in cell_sizes):
         raise NotImplementedError("Negative cell sizes not supported.")
 
-    ls = np.log2(n_cell_dim).astype(int)
-
-    if len(set(ls)) == 1:
-        max_level = ls[0]
-    else:
-        max_level = min(ls) + 1
-
+    levels = tree_levels(mesh)
     cells = np.vstack(mesh.octree_cells.tolist())
     indexes = cells[:, :-1] * 2 + cells[:, -1][:, None]  # convert to cpp index
-    levels = max_level - np.log2(cells[:, -1])
     treemesh = TreeMesh(
         cell_sizes, x0=np.asarray(mesh.origin.tolist()), diagonal_balance=False
     )
@@ -620,6 +612,30 @@ def octree_2_treemesh(  # pylint: disable=too-many-locals
     return treemesh
 
 
+def tree_levels(mesh: Octree) -> np.ndarray | None:
+    """
+    Convert Octree n cell indices to Treemesh level indices.
+
+    :param mesh: Octree object with n cell index.
+
+    :returns: Array of level indices.
+    """
+    if mesh.octree_cells is None:
+        return None
+
+    n_cell_dim = [mesh.u_count, mesh.v_count, mesh.w_count]
+    ls = np.log2(n_cell_dim).astype(int)
+
+    if len(set(ls)) == 1:
+        max_level = ls[0]
+    else:
+        max_level = min(ls) + 1
+
+    levels = max_level - np.log2(mesh.octree_cells["NCells"])
+
+    return levels.astype(int)
+
+
 def resample_locations(locations: np.ndarray, increment: float) -> np.ndarray:
     """
     Resample locations along a sequence of positions at a given increment.
diff --git a/tests/utils_test.py b/tests/utils_test.py
index 8db5f73..dac264b 100644
--- a/tests/utils_test.py
+++ b/tests/utils_test.py
@@ -30,6 +30,7 @@
     octree_2_treemesh,
     surface_strip,
     tensor_mesh_ordering,
+    tree_levels,
     treemesh_2_octree,
 )
 
@@ -242,7 +243,7 @@ def test_find_endpoints():
 
 
 def test_surface_strip(tmp_path):
-    with Workspace.create(tmp_path / "test.geoh5") as workspace:
+    with Workspace.create(tmp_path / f"{__name__}.geoh5") as workspace:
         line = Points.create(
             workspace, vertices=np.array([[-1, 0, 0], [0, 0, 0], [1, 0, 0]])
         )
@@ -282,7 +283,7 @@ def test_not_implemented_negative():
 
 
 def test_collocate_octrees(tmp_path: Path):
-    with Workspace.create(tmp_path / "test.geoh5") as workspace:
+    with Workspace.create(tmp_path / f"{__name__}.geoh5") as workspace:
         local_mesh1 = TreeMesh(
             [[10] * 16, [10] * 16, [10] * 16], [1000, 0, 0], diagonal_balance=True
         )
@@ -391,7 +392,7 @@ def test_create_octree_from_octrees_errors():
 
 
 def test_densify_curve(tmp_path: Path):
-    with Workspace.create(tmp_path / "test.geoh5") as workspace:
+    with Workspace.create(tmp_path / f"{__name__}.geoh5") as workspace:
         curve = Curve.create(
             workspace,
             vertices=np.vstack([[0, 0, 0], [10, 0, 0], [10, 10, 0]]),
@@ -490,8 +491,43 @@ def test_octree_2_treemesh():
         np.testing.assert_allclose(tmesh.cell_centers, mesh.cell_centers)
 
 
+def test_tree_levels(tmp_path):
+    with Workspace.create(tmp_path / f"{__name__}.geoh5") as workspace:
+        mesh = Octree.create(
+            workspace,
+            name="test",
+            origin=[0, 0, 0],
+            u_count=8,
+            v_count=8,
+            w_count=8,
+            u_cell_size=10.0,
+            v_cell_size=20.0,
+            w_cell_size=40.0,
+            octree_cells=np.array(
+                [
+                    [0, 0, 0, 2],
+                    [2, 0, 0, 2],
+                    [0, 2, 0, 2],
+                    [2, 2, 0, 2],
+                    [0, 0, 2, 2],
+                    [2, 0, 2, 2],
+                    [0, 2, 2, 2],
+                    [2, 2, 2, 2],
+                    [4, 0, 0, 4],
+                    [0, 4, 0, 4],
+                    [4, 4, 0, 4],
+                ]
+            ),
+        )
+
+        levels = tree_levels(mesh)
+        assert levels[-1] == 1  # Largest cell
+        assert levels[0] == 2  # Medium size
+        assert np.all(levels < 3)  # No highest level
+
+
 def test_roundtrip_octree_conversion(tmp_path):
-    with Workspace.create(tmp_path / "test.geoh5") as workspace:
+    with Workspace.create(tmp_path / f"{__name__}.geoh5") as workspace:
         points = np.vstack(
             [
                 [10, 10, -10],