diff --git a/compound_interest.py b/compound_interest.py
index 9673a7a029..d014ffa3b8 100755
--- a/compound_interest.py
+++ b/compound_interest.py
@@ -13,7 +13,7 @@
 
 
 def compound_interest(p, t, r):
-    return p * (pow((1 + r / 100), t))
+    return p * (pow((1 + r / 100), t)) - p
 
 
 if __name__ == "__main__":