How to resize (height and width) of an IconButton in Flutter

You can force it to size itself with the SizedBox.

new SizedBox(
   height: 18.0,
   width: 18.0,
   child: new IconButton(
      padding: new EdgeInsets.all(0.0),
      color: themeData.primaryColor,
      icon: new Icon(Icons.clear, size: 18.0),
      onPressed: onDelete,
   )
)