diff --git a/src/blenderbim/blenderbim/bim/module/pset/calc_quantity_function_mapper.py b/src/blenderbim/blenderbim/bim/module/pset/calc_quantity_function_mapper.py
index f30b82a8f2..5bdefe8f52 100644
--- a/src/blenderbim/blenderbim/bim/module/pset/calc_quantity_function_mapper.py
+++ b/src/blenderbim/blenderbim/bim/module/pset/calc_quantity_function_mapper.py
@@ -291,7 +291,7 @@ mapper = {
         'GrossSurfaceArea' : "get_gross_surface_area",
         'GrossVolume' : "get_gross_volume",
         'NetVolume' : "get_net_volume",
-        'GrossWeight' : None,
+        'GrossWeight' : "get_gross_weight",
         'NetWeight' : None,
     },
     'Qto_PumpBaseQuantities' : {
@@ -386,7 +386,7 @@ mapper = {
         'NetSideArea' : "get_net_side_area",
         'GrossVolume' : "get_gross_volume",
         'NetVolume' : "get_net_volume",
-        'GrossWeight' : None,
+        'GrossWeight' : "get_gross_weight",
         'NetWeight' : None,
     },
     'Qto_StairFlightBaseQuantities' : {
@@ -476,7 +476,7 @@ mapper = {
         'NetSurfaceArea' : "get_net_surface_area",
         'GrossVolume' : "get_gross_volume",
         'NetVolume' : "get_net_volume",
-        'GrossWeight' : None,
+        'GrossWeight' : "get_gross_weight",
         'NetWeight' : None,
     },
     'Qto_SleeperBaseQuantities' : {
diff --git a/src/blenderbim/blenderbim/bim/module/pset/qto_calculator.py b/src/blenderbim/blenderbim/bim/module/pset/qto_calculator.py
index 2e26330fc1..9a778e3e3c 100644
--- a/src/blenderbim/blenderbim/bim/module/pset/qto_calculator.py
+++ b/src/blenderbim/blenderbim/bim/module/pset/qto_calculator.py
@@ -472,6 +472,63 @@ class QtoCalculator:
         decompositions = ifcopenshell.util.element.get_decomposition(element)
         return decompositions
 
+    def get_gross_weight(self, obj):
+        obj_mass_density = self.get_obj_mass_density(obj)
+        if not obj_mass_density:
+            return
+        gross_volume = self.get_gross_volume(obj)
+        gross_weight = obj_mass_density * gross_volume
+        return gross_weight
+
+    def get_obj_mass_density(self, obj):
+        entity = tool.Ifc.get_entity(obj)
+        material = ifcopenshell.util.element.get_material(entity)
+        if (
+            material.is_a("IfcMaterialLayerSet")
+            or material.is_a("IfcMaterialProfileSet")
+            or material.is_a("IfcMaterialConstituentSet")
+        ):
+                return
+
+        if material.is_a('IfcMaterial'):
+            obj_mass_density = self.get_single_material_mass_density(material)
+            return obj_mass_density
+
+        if material.is_a('IfcMaterialLayerSetUsage'):
+            material_layers = material.ForLayerSet.MaterialLayers
+            densities = []
+            thicknesses = []
+            obj_mass_density = 0
+            for material_layer in material_layers:
+                density = self.get_single_material_mass_density(material_layer.Material)
+                if density is None:
+                    return
+                densities.append(density)
+                thickness = material_layer.LayerThickness
+                thicknesses.append(thickness)
+                obj_mass_density = obj_mass_density + (density * thickness)
+            total_thickness = sum(thicknesses)
+            obj_mass_density = obj_mass_density/total_thickness
+            return obj_mass_density
+
+        if material.is_a('IfcMaterialProfileSetUsage'):
+            material_profiles = material.ForProfileSet.MaterialProfiles
+            if len(material_profiles) == 1:
+                obj_mass_density = self.get_single_material_mass_density(material_profiles[0].Material)
+                return obj_mass_density
+            else:
+                return
+
+
+    def get_single_material_mass_density(self, material):
+        for material_property in material.HasProperties:
+            if "Pset_MaterialCommon" in material_property.Name:
+                for prop in material_property.Properties:
+                    if "MassDensity" in prop:
+                        return prop.NominalValue.wrappedValue
+            else:
+                return
+
 
 
     # The following is @Moult's older code.  Keeping it here just in case the bmesh function is buggy. -vulevukusej
diff --git a/src/blenderbim/blenderbim/tool/qto.py b/src/blenderbim/blenderbim/tool/qto.py
index a10882ab9b..290354d5ae 100644
--- a/src/blenderbim/blenderbim/tool/qto.py
+++ b/src/blenderbim/blenderbim/tool/qto.py
@@ -90,7 +90,7 @@ class Qto(blenderbim.core.tool.Qto):
         return {
             quantity_name: cls.get_rounded_value(calculator.calculate_quantity(qto_name, quantity_name, obj))
             for quantity_name in cls.get_applicable_quantity_names(qto_name) or []
-            if cls.has_calculator(qto_name, quantity_name)
+            if cls.has_calculator(qto_name, quantity_name) and calculator.calculate_quantity(qto_name, quantity_name, obj) is not None
         }
 
     @classmethod