diff --git a/Controller/MainController.py b/Controller/MainController.py
index 5fb7f6e..24e3f2a 100644
--- a/Controller/MainController.py
+++ b/Controller/MainController.py
@@ -115,6 +115,9 @@ def model_changed(self):
         self.main_widget.spectrum_widget.plot_sq(self.model.sq_spectrum)
         self.main_widget.spectrum_widget.plot_pdf(self.model.gr_spectrum)
 
+        self.main_widget.left_control_widget.composition_widget.density_atomic_units_lbl.\
+            setText("{:.4f}".format(self.model.atomic_density))
+
 
     def bkg_scale_changed(self, value):
         self.model.background_scaling = value
diff --git a/Models/GlassureModel.py b/Models/GlassureModel.py
index df3989d..ed63619 100644
--- a/Models/GlassureModel.py
+++ b/Models/GlassureModel.py
@@ -47,6 +47,13 @@ def load_bkg(self, filename):
         self.background_spectrum.load(filename)
         self.calculate_spectra()
 
+    @property
+    def atomic_density(self):
+        if len(self.composition):
+            return convert_density_to_atoms_per_cubic_angstrom(self.composition, self.density)
+        return 0
+
+
     @property
     def background_spectrum(self):
         if self.diamond_background_spectrum is None:
@@ -73,7 +80,6 @@ def set_smooth(self, value):
 
     def update_parameter(self, composition, density, q_min, q_max, r_cutoff, r_min, r_max, use_modification_fcn=False,
                          interpolation_method=None, interpolation_parameters=None):
-        print "update"
         self.composition = composition
         self.density = density
 
diff --git a/Views/ControlWidgets/CompositionWidget.py b/Views/ControlWidgets/CompositionWidget.py
index 2c5b3b9..c7f8200 100644
--- a/Views/ControlWidgets/CompositionWidget.py
+++ b/Views/ControlWidgets/CompositionWidget.py
@@ -10,49 +10,61 @@ class CompositionWidget(QtGui.QWidget):
 
     def __init__(self, *args):
         super(CompositionWidget, self).__init__(*args)
-        self.create_widgets()
 
-    def create_widgets(self):
+        self._create_widgets()
+        self._create_layout()
+        self._style_widgets()
+
+    def _create_widgets(self):
+        self.add_element_btn = QtGui.QPushButton("Add")
+        self.delete_element_btn = QtGui.QPushButton("Delete")
+
+        self.density_lbl = QtGui.QLabel("Density:")
+        self.density_txt = QtGui.QLineEdit("2.2")
+        self.density_atomic_units_lbl = QtGui.QLabel("")
+
+        self.composition_tw = QtGui.QTableWidget()
+        self.composition_tw.cellChanged.connect(self.emit_composition_changed_signal)
+
+    def _create_layout(self):
         self.main_layout = QtGui.QVBoxLayout()
         self.main_layout.setContentsMargins(0, 0, 0, 0)
         self.main_layout.setSpacing(5)
 
         self.button_layout = QtGui.QHBoxLayout()
         self.button_layout.setSpacing(15)
-        self.add_element_btn = QtGui.QPushButton("Add")
-        self.delete_element_btn = QtGui.QPushButton("Delete")
         self.button_layout.addWidget(self.add_element_btn)
         self.button_layout.addWidget(self.delete_element_btn)
 
-        self.density_layout = QtGui.QHBoxLayout()
-        self.density_lbl = QtGui.QLabel("Density:")
+        self.density_layout = QtGui.QGridLayout()
+        self.density_layout.addWidget(self.density_lbl, 0, 0)
+        self.density_layout.addWidget(self.density_txt, 0, 1)
+        self.density_layout.addWidget(QtGui.QLabel('g/cm^3'), 0, 2)
+        self.density_layout.addWidget(self.density_atomic_units_lbl, 1, 1)
+        self.density_layout.addWidget(QtGui.QLabel('at/A^3'), 1, 2)
+
+        self.main_layout.addLayout(self.button_layout)
+        self.main_layout.addWidget(self.composition_tw)
+        self.main_layout.addLayout(self.density_layout)
+
+        self.setLayout(self.main_layout)
+
+
+    def _style_widgets(self):
         self.density_lbl.setAlignment(QtCore.Qt.AlignVCenter | QtCore.Qt.AlignRight)
-        self.density_txt = QtGui.QLineEdit("2.2")
+        self.density_atomic_units_lbl.setAlignment(QtCore.Qt.AlignVCenter | QtCore.Qt.AlignRight)
+
         self.density_txt.setAlignment(QtCore.Qt.AlignRight)
         self.density_txt.setValidator(QtGui.QDoubleValidator())
         self.density_txt.editingFinished.connect(self.emit_composition_changed_signal)
         self.density_txt.setMaximumWidth(100)
-        self.density_error_lbl = QtGui.QLabel("NaN")
-        self.density_layout.addWidget(self.density_lbl)
-        self.density_layout.addWidget(self.density_txt)
-        self.density_layout.addWidget(QtGui.QLabel('+-'))
-        self.density_layout.addWidget(self.density_error_lbl)
-        self.density_layout.addWidget(QtGui.QLabel('g/cm^3'))
 
-        self.composition_tw = QtGui.QTableWidget()
         self.composition_tw.setColumnCount(2)
         self.composition_tw.horizontalHeader().setVisible(False)
         self.composition_tw.verticalHeader().setVisible(False)
         self.composition_tw.setColumnWidth(0, 80)
         self.composition_tw.setColumnWidth(1, 80)
         self.composition_tw.setItemDelegate(TextDoubleDelegate(self))
-        self.composition_tw.cellChanged.connect(self.emit_composition_changed_signal)
-
-        self.main_layout.addLayout(self.button_layout)
-        self.main_layout.addWidget(self.composition_tw)
-        self.main_layout.addLayout(self.density_layout)
-
-        self.setLayout(self.main_layout)
 
     def add_element(self, element=None, value=None):
         current_rows = self.composition_tw.rowCount()