diff --git a/include/sys/param.h b/include/sys/param.h
index 4e94f51bbc..831a552eae 100644
--- a/include/sys/param.h
+++ b/include/sys/param.h
@@ -43,6 +43,14 @@
 #  define MAX(a,b)      (((a) > (b)) ? (a) : (b))
 #endif  /* MAX */
 
+/* Macros for number of items.
+ * (aka. ARRAY_SIZE, ArraySize, Size of an Array)
+ */
+
+#ifndef nitems
+#  define nitems(_a)    (sizeof(_a) / sizeof(0[(_a)]))
+#endif /* nitems */
+
 /****************************************************************************
  * Public Type Definitions
  ****************************************************************************/