diff --git a/aero_astro_calc/Inertia.py b/aero_astro_calc/Inertia.py
new file mode 100644
index 0000000..535e556
--- /dev/null
+++ b/aero_astro_calc/Inertia.py
@@ -0,0 +1,14 @@
+from typing import Tuple
+
+
+class Inertia:
+    def __init__(self, area: float, centroid: Tuple[float, float]):
+        self.area = area
+        self.centroid = centroid
+
+    def __add__(self, other):
+        AX = self.area * self.centroid[0] + other.area * other.centroid[0]
+        AY = self.area * self.centroid[1] + other.area * other.centroid[1]
+        self.area = self.area + other.area
+        self.centroid = (AX / self.area, AY / self.area)
+