Index: src/wp-includes/default-constants.php
===================================================================
--- src/wp-includes/default-constants.php	(revision 35278)
+++ src/wp-includes/default-constants.php	(working copy)
@@ -107,6 +107,18 @@
 	define( 'MONTH_IN_SECONDS',  30 * DAY_IN_SECONDS    );
 	define( 'YEAR_IN_SECONDS',  365 * DAY_IN_SECONDS    );
 	/**#@-*/
+
+	/**#@+
+	 * Constants for expressing human-readable data sizes
+	 * in their respective number of bytes.
+	 *
+	 * @since 4.4
+	 */
+	define( 'KB_IN_BYTES', 1024 );
+	define( 'MB_IN_BYTES', 1024 * KB_IN_BYTES );
+	define( 'GB_IN_BYTES', 1024 * MB_IN_BYTES );
+	define( 'TB_IN_BYTES', 1024 * GB_IN_BYTES );
+	/**#@-*/
 }
 
 /**