diff --git a/include/rexy/mpmc_queue.hpp b/include/rexy/mpmc_queue.hpp
index 60fb11c..26f8f48 100644
--- a/include/rexy/mpmc_queue.hpp
+++ b/include/rexy/mpmc_queue.hpp
@@ -122,6 +122,8 @@ namespace rexy{
 
 		void pop(reference t);
 		bool try_pop(reference t);
+
+		size_type size(void)const;
 	private:
 		constexpr size_type rotation_cnt(size_type t);
 	};
diff --git a/include/rexy/mpmc_queue.tpp b/include/rexy/mpmc_queue.tpp
index ec5fa78..7c183d5 100644
--- a/include/rexy/mpmc_queue.tpp
+++ b/include/rexy/mpmc_queue.tpp
@@ -209,6 +209,10 @@ namespace rexy{
 		}
 	}
 	template<class T>
+	auto mpmc_queue<T>::size(void)const -> size_type{
+		return m_slots.size();
+	}
+	template<class T>
 	constexpr auto mpmc_queue<T>::rotation_cnt(size_type t) -> size_type{
 		return (t / m_slots.capacity());
 	}