diff --git a/src/wp-includes/default-constants.php b/src/wp-includes/default-constants.php
index 795b9190dd..252c98e40b 100644
--- a/src/wp-includes/default-constants.php
+++ b/src/wp-includes/default-constants.php
@@ -107,6 +107,17 @@ function wp_initial_constants() {
 	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 4.4.0
+	 */
+	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 );
+	/**#@-*/
 }
 
 /**