diff --git a/src/calibre/gui2/book_details.py b/src/calibre/gui2/book_details.py
index 609c2b30f3..6c3dae3c94 100644
--- a/src/calibre/gui2/book_details.py
+++ b/src/calibre/gui2/book_details.py
@@ -483,8 +483,15 @@ class BookDetails(QWidget): # {{{
         self.book_info.show_data(data)
         self.cover_view.show_data(data)
         self._layout.do_layout(self.rect())
-        self.setToolTip('<p>'+_('Double-click to open Book Details window') +
-                '<br><br>' + _('Path') + ': ' + data.get(_('Path'), ''))
+        try:
+            sz = self.cover_view.pixmap.size()
+        except:
+            sz = QSize(0, 0)
+        self.setToolTip(
+                '<p>'+_('Double-click to open Book Details window') +
+                '<br><br>' + _('Path') + ': ' + data.get(_('Path'), '') +
+                '<br><br>' + _('Cover size: %dx%d')%(sz.width(), sz.height())
+        )
 
     def reset_info(self):
         self.show_data({})
diff --git a/src/calibre/gui2/dialogs/book_info.py b/src/calibre/gui2/dialogs/book_info.py
index e860579fdf..46d26c2f4a 100644
--- a/src/calibre/gui2/dialogs/book_info.py
+++ b/src/calibre/gui2/dialogs/book_info.py
@@ -109,6 +109,8 @@ class BookInfo(QDialog, Ui_BookInfo):
                 pixmap = pixmap.scaled(new_width, new_height,
                         Qt.KeepAspectRatio, Qt.SmoothTransformation)
         self.cover.set_pixmap(pixmap)
+        sz = pixmap.size()
+        self.cover.setToolTip(_('Cover size: %dx%d')%(sz.width(), sz.height()))
 
     def refresh(self, row):
         if isinstance(row, QModelIndex):