diff --git a/src/obitypes.c b/src/obitypes.c
new file mode 100644
index 0000000..06c9120
--- /dev/null
+++ b/src/obitypes.c
@@ -0,0 +1,53 @@
+/*
+ * obitypes.c
+ *
+ *  Created on: 23 mai 2015
+ *      Author: coissac
+ */
+
+#include <obitypes.h>
+
+size_t obi_sizeof(OBIType_t type) {
+	size_t size=0
+
+	switch (type) {
+	case OBI_VOID:  size = 1;
+					break;
+
+	case OBI_INT:   size = sizeof(obiint_t);
+					break;
+
+	case OBI_FLOAT: size = sizeof(obifloat_t);
+					break;
+
+	case OBI_CHAR:  size = sizeof(obichar_t);
+					break;
+
+	case OBI_IDX:   size = sizeof(obiidx_t);
+					break;
+
+	default:        size = 0;
+	}
+
+	return size;
+}
+
+
+size_t obi_array_sizeof(OBIType_t type,size_t nbelement) {
+	size_t size;
+	size_t rsize;
+	size_t psize;
+
+	size = obi_sizeof(type) * nbelement;
+
+	psize= getpagesize();
+	rsize= size % psize;
+
+	// Round at a size multiple of pagesize
+	if (rsize)
+		size = (size / psize) * psize + psize;
+
+
+	return size;
+}
+
diff --git a/src/obitypes.h b/src/obitypes.h
index 96ce6c9..0d32191 100644
--- a/src/obitypes.h
+++ b/src/obitypes.h
@@ -1,7 +1,3 @@
-/****************************************************************************
- * OBITypes header file                                                     *
- ****************************************************************************/
-
 /**
  * @file obitypes.h
  * @author Celine Mercier
@@ -13,6 +9,7 @@
 #define OBITYPES_H_
 
 #include <stdio.h>
+#include <unistd.h>
 
 #define OBIInt_NA (INT32_MIN)
 #define OBIFloat_NA (NAN)
@@ -35,10 +32,10 @@ typedef enum {
 
 typedef enum OBIType {
 	OBI_VOID    = 0,     		/**< data type not specified */
-	OBIInt_t,					/**< a signed integer value (C type : int32_t) */
-	OBIFloat_t,					/**< a floating value (C type : double) */
-	OBIChar_t,					/**< a character (C type : char) */
-	OBIIdx_t					/**< an index in a data structure (C type : size_t) */
+	OBI_INT,			    	/**< a signed integer value (C type : int32_t) */
+	OBI_FLOAT,					/**< a floating value (C type : double) */
+	OBI_CHAR,					/**< a character (C type : char) */
+	OBI_IDX					    /**< an index in a data structure (C type : size_t) */
 } OBIType_t, *OBIType_p;
 
 typedef int32_t obiint_t;
@@ -46,5 +43,34 @@ typedef double obifloat_t;
 typedef char obichar_t;
 typedef size_t obiidx_t;
 
+/**
+ * @brief returns the memory size in bytes of an OBIType
+ *
+ * @param type the OBIType code used as query
+ *
+ * @return the size in bytes of the type
+ * @retval 0 on error (unknown type)
+ *
+ * @since May 2015
+ * @author Eric Coissac (eric.coissac@metabarcoding.org)
+ */
+size_t obi_sizeof(OBIType_t type);
+
+/**
+ * @brief returns the size requested to store an array of OBIType
+ *
+ * The returned size is enouth large to store an array of size nbelement
+ * but rounded at a multiple of the memory page size.
+ *
+ * @param type the OBIType code used as query
+ * @param nbelement the number of element to be stored
+ *
+ * @return the size in bytes of the type
+ * @retval 0 on error (unknown type)
+ *
+ * @since May 2015
+ * @author Eric Coissac (eric.coissac@metabarcoding.org)
+ */
+size_t obi_array_sizeof(OBIType_t type,size_t nbelement);
 
 #endif /* OBITYPES_H_ */