diff --git a/ccv/sheet4/gauss_pyramid.cpp b/ccv/sheet4/gauss_pyramid.cpp
index c0640ec..03059ee 100644
--- a/ccv/sheet4/gauss_pyramid.cpp
+++ b/ccv/sheet4/gauss_pyramid.cpp
@@ -19,3 +19,8 @@ cv::Mat gauss_pyramid::get(int layer)
 {
   return _layers.at((unsigned long) layer);
 }
+
+unsigned long gauss_pyramid::get_number_of_layers()
+{
+  return _layers.size();
+}
diff --git a/ccv/sheet4/gauss_pyramid.h b/ccv/sheet4/gauss_pyramid.h
index 6249c1a..4583332 100644
--- a/ccv/sheet4/gauss_pyramid.h
+++ b/ccv/sheet4/gauss_pyramid.h
@@ -11,6 +11,7 @@ public:
     gauss_pyramid();
     gauss_pyramid(cv::Mat img, float sigma, int number_of_layers);
     cv::Mat get(int layer);
+    unsigned long get_number_of_layers();
 };