diff --git a/Eci.cpp b/Eci.cpp
index 4d09aae..266a3f5 100644
--- a/Eci.cpp
+++ b/Eci.cpp
@@ -21,12 +21,12 @@ Eci::Eci(const Julian &date, const CoordGeodetic &geo)
     position_.SetY(achcp * sin(theta));
 
     position_.SetZ((Globals::XKMPER() * s + altitude) * sin(latitude));
-    position_.SetW(sqrt(pow(position_.GetX(), 2.0) + pow(position_.GetY(), 2.0) + pow(position_.GetZ(), 2.0)));
+    position_.SetW(position_.GetMagnitude());
 
     velocity_.SetX(-mfactor * position_.GetY());
     velocity_.SetY(mfactor * position_.GetX());
     velocity_.SetZ(0.0);
-    velocity_.SetW(sqrt(pow(velocity_.GetX(), 2.0) + pow(velocity_.GetY(), 2.0)));
+    velocity_.SetW(velocity_.GetMagnitude());
 }
 
 Eci::Eci(const Julian &date, const Vector &position, const Vector &velocity)
diff --git a/Vector.cpp b/Vector.cpp
index 37e7137..183fd91 100644
--- a/Vector.cpp
+++ b/Vector.cpp
@@ -1 +1,5 @@
 #include "Vector.h"
+
+double Vector::GetMagnitude() const {
+    return sqrt(x_ * x_ + y_ * y_ + z_ * z_);
+}
diff --git a/Vector.h b/Vector.h
index ed8c16d..2b2bb8c 100644
--- a/Vector.h
+++ b/Vector.h
@@ -1,6 +1,8 @@
 #ifndef VECTOR_H_
 #define VECTOR_H_
 
+#include <cmath>
+
 class Vector {
 public:
 
@@ -43,6 +45,8 @@ public:
         return w_;
     }
 
+    double GetMagnitude() const;
+
 protected:
     double x_;
     double y_;