diff --git a/Modules/Core/Common/include/itkNumericTraits.h b/Modules/Core/Common/include/itkNumericTraits.h
index 65dcdaf3f7a..16ce69396e2 100644
--- a/Modules/Core/Common/include/itkNumericTraits.h
+++ b/Modules/Core/Common/include/itkNumericTraits.h
@@ -198,14 +198,14 @@ class NumericTraits : public std::numeric_limits<T>
    * VariableLengthVector will provide a different implementation
    * where a vector of the correct size is built.
    */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const T &)
   {
     return GetLength();
   }
 
   /** Return the length of the scalar: 1. Array types can return a different value */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return 1;
diff --git a/Modules/Core/Common/include/itkNumericTraitsCovariantVectorPixel.h b/Modules/Core/Common/include/itkNumericTraitsCovariantVectorPixel.h
index 95bff64b64f..581a5745446 100644
--- a/Modules/Core/Common/include/itkNumericTraitsCovariantVectorPixel.h
+++ b/Modules/Core/Common/include/itkNumericTraitsCovariantVectorPixel.h
@@ -161,14 +161,14 @@ class NumericTraits<CovariantVector<T, D>>
   }
 
   /** Return the length of the vector. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const CovariantVector<T, D> &)
   {
     return D;
   }
 
   /** Return the length of the vector. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return D;
diff --git a/Modules/Core/Common/include/itkNumericTraitsDiffusionTensor3DPixel.h b/Modules/Core/Common/include/itkNumericTraitsDiffusionTensor3DPixel.h
index 0956137270f..809c41aaec0 100644
--- a/Modules/Core/Common/include/itkNumericTraitsDiffusionTensor3DPixel.h
+++ b/Modules/Core/Common/include/itkNumericTraitsDiffusionTensor3DPixel.h
@@ -163,14 +163,14 @@ class NumericTraits<DiffusionTensor3D<T>>
   }
 
   /** Return the size of the tensor. Always returns 6. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const DiffusionTensor3D<T> &)
   {
     return 6;
   }
 
   /** Return the size of the tensor. Always returns 6. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return 6;
diff --git a/Modules/Core/Common/include/itkNumericTraitsFixedArrayPixel.h b/Modules/Core/Common/include/itkNumericTraitsFixedArrayPixel.h
index 3e5ec2590e1..0b2843c0100 100644
--- a/Modules/Core/Common/include/itkNumericTraitsFixedArrayPixel.h
+++ b/Modules/Core/Common/include/itkNumericTraitsFixedArrayPixel.h
@@ -157,14 +157,14 @@ class NumericTraits<FixedArray<T, D>>
   }
 
   /** Return the length of the array. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const FixedArray<T, D> &)
   {
     return D;
   }
 
   /** Return the length of the array. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return D;
diff --git a/Modules/Core/Common/include/itkNumericTraitsPointPixel.h b/Modules/Core/Common/include/itkNumericTraitsPointPixel.h
index 53b2217f87f..08eb781e56a 100644
--- a/Modules/Core/Common/include/itkNumericTraitsPointPixel.h
+++ b/Modules/Core/Common/include/itkNumericTraitsPointPixel.h
@@ -148,14 +148,14 @@ class NumericTraits<Point<T, D>>
   }
 
   /** Return the dimensionality of the point. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const Point<T, D> &)
   {
     return D;
   }
 
   /** Return the dimensionality of the point. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return D;
diff --git a/Modules/Core/Common/include/itkNumericTraitsRGBAPixel.h b/Modules/Core/Common/include/itkNumericTraitsRGBAPixel.h
index 196cd03c143..422a5da8831 100644
--- a/Modules/Core/Common/include/itkNumericTraitsRGBAPixel.h
+++ b/Modules/Core/Common/include/itkNumericTraitsRGBAPixel.h
@@ -188,14 +188,14 @@ class NumericTraits<RGBAPixel<T>>
   }
 
   /** Return the dimensionality of the pixel. Always returns 4. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const RGBAPixel<T> &)
   {
     return 4;
   }
 
   /** Return the dimensionality of the pixel. Always returns 4. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return 4;
diff --git a/Modules/Core/Common/include/itkNumericTraitsRGBPixel.h b/Modules/Core/Common/include/itkNumericTraitsRGBPixel.h
index ff4321f8fc5..4a5884415ce 100644
--- a/Modules/Core/Common/include/itkNumericTraitsRGBPixel.h
+++ b/Modules/Core/Common/include/itkNumericTraitsRGBPixel.h
@@ -188,14 +188,14 @@ class NumericTraits<RGBPixel<T>>
   }
 
   /** Return the dimensionality of the pixel. Always returns 3. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const RGBPixel<T> &)
   {
     return 3;
   }
 
   /** Return the dimensionality of the pixel. Always returns 3. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return 3;
diff --git a/Modules/Core/Common/include/itkNumericTraitsTensorPixel.h b/Modules/Core/Common/include/itkNumericTraitsTensorPixel.h
index 57eb4be881d..6251d0c19f3 100644
--- a/Modules/Core/Common/include/itkNumericTraitsTensorPixel.h
+++ b/Modules/Core/Common/include/itkNumericTraitsTensorPixel.h
@@ -163,14 +163,14 @@ class NumericTraits<SymmetricSecondRankTensor<T, D>>
   }
 
   /** Return the size of the underlying FixedArray. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const SymmetricSecondRankTensor<T, D> &)
   {
     return GetLength();
   }
 
   /** Return the size of the underlying FixedArray. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return D * (D + 1) / 2;
diff --git a/Modules/Core/Common/include/itkNumericTraitsVectorPixel.h b/Modules/Core/Common/include/itkNumericTraitsVectorPixel.h
index b705717e0d3..4491be35c0c 100644
--- a/Modules/Core/Common/include/itkNumericTraitsVectorPixel.h
+++ b/Modules/Core/Common/include/itkNumericTraitsVectorPixel.h
@@ -203,14 +203,14 @@ class NumericTraits<Vector<T, D>>
   }
 
   /** Return the size of the vector. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength(const Vector<T, D> &)
   {
     return D;
   }
 
   /** Return the size of the vector. */
-  static unsigned int
+  static constexpr unsigned int
   GetLength()
   {
     return D;