diff --git a/cpp/Pose3.h b/cpp/Pose3.h
index 106e882c5..4db5ff3ee 100644
--- a/cpp/Pose3.h
+++ b/cpp/Pose3.h
@@ -61,6 +61,9 @@ namespace gtsam {
 
     Pose3 transform_to(const Pose3& pose) const;
 
+    /** get the dimension by the type */
+    static inline size_t dim() { return 6; };
+
   private:
     /** Serialization function */
     friend class boost::serialization::access;
diff --git a/cpp/Rot2.h b/cpp/Rot2.h
index 40e3858a3..12de03caa 100644
--- a/cpp/Rot2.h
+++ b/cpp/Rot2.h
@@ -75,6 +75,9 @@ namespace gtsam {
     /** rotate from world to rotated = R'*p */
     Point2 unrotate(const Point2& p) const;
 
+    /** get the dimension by the type */
+    static inline size_t dim() { return 1; };
+
   private:
     /** Serialization function */
     friend class boost::serialization::access;
diff --git a/cpp/Rot3.h b/cpp/Rot3.h
index f41bc7816..0c42dd09d 100644
--- a/cpp/Rot3.h
+++ b/cpp/Rot3.h
@@ -106,6 +106,9 @@ namespace gtsam {
      */
     Vector ypr() const;
 
+    /** get the dimension by the type */
+    static inline size_t dim() { return 3; };
+
   private:
     /** Serialization function */
     friend class boost::serialization::access;