diff --git a/aabb.cpp b/aabb.cpp
index 3bb07aac..c18a0699 100644
--- a/aabb.cpp
+++ b/aabb.cpp
@@ -30,6 +30,15 @@ AABB<S,T>::AABB (point<S,T> _p0, point<S,T> _p1):
 }
 
 
+//-----------------------------------------------------------------------------
+template <size_t S, typename T>
+T
+AABB<S,T>::diameter (void) const
+{
+    return magnitude ().diameter ();
+}
+
+
 //-----------------------------------------------------------------------------
 template <size_t S, typename T>
 util::extent<S,T>
diff --git a/aabb.hpp b/aabb.hpp
index 2715c65f..01d51881 100644
--- a/aabb.hpp
+++ b/aabb.hpp
@@ -30,6 +30,7 @@ namespace util {
         AABB () = default;
         AABB (point<S,T>, point<S,T>);
 
+        T diameter (void) const;
         extent<S,T> magnitude (void) const;
 
         bool overlaps (point<S,T>) const;