diff --git a/docs/source_docs/user_guide/inputs/output/monitors.rst b/docs/source_docs/user_guide/inputs/output/monitors.rst
index 6a5bda130e8ec281009fa527443da481d42778ce..1ff27e1d1d241c425a59fb6713c5268859f3e9a3 100644
--- a/docs/source_docs/user_guide/inputs/output/monitors.rst
+++ b/docs/source_docs/user_guide/inputs/output/monitors.rst
@@ -522,12 +522,24 @@ Sum
 
    .. math:: \sum_p w_p \phi_p
 
+Mass-Weighted Sum
+
+   +----------------------------------------------+
+   | Lagrangian::GeneralProperty::MassWeightedSum |
+   +----------------------------------------------+
+
+   The mass-weighted sum of particle property, :math:`\phi_p` in the selected region is
+   calculated using the following expression.
+
+   .. math:: \sum_p w_p m_p \phi_p
+
+
 Min
    +----------------------------------+
    | Lagrangian::GeneralProperty::Min |
    +----------------------------------+
 
-   The minimum value of particle property :math:`phi_p` is the selected region
+   The minimum value of particle property :math:`\phi_p` is the selected region
    is obtained using the following expression.
 
    .. math:: \min_p \phi_p
@@ -537,7 +549,7 @@ Max
    | Lagrangian::GeneralProperty::Max |
    +----------------------------------+
 
-   The maximum value of particle property :math:`phi_p` is the selected region
+   The maximum value of particle property :math:`\phi_p` is the selected region
    is obtained using the following expression.
 
    .. math:: \max_p \phi_p