diff --git a/src/calibre/gui2/convert/single.py b/src/calibre/gui2/convert/single.py
index 332dc4ae92..cff7ee8c3d 100644
--- a/src/calibre/gui2/convert/single.py
+++ b/src/calibre/gui2/convert/single.py
@@ -33,7 +33,10 @@ from calibre.utils.config import prefs
 from calibre.utils.logging import Log
 
 class NoSupportedInputFormats(Exception):
-    pass
+
+    def __init__(self, available_formats):
+        Exception.__init__(self)
+        self.available_formats = available_formats
 
 def sort_formats_by_preference(formats, prefs):
     uprefs = [x.upper() for x in prefs]
@@ -86,7 +89,7 @@ def get_supported_input_formats_for_book(db, book_id):
     input_formats = set([x.lower() for x in supported_input_formats()])
     input_formats = sorted(available_formats.intersection(input_formats))
     if not input_formats:
-        raise NoSupportedInputFormats
+        raise NoSupportedInputFormats(tuple(x for x in available_formats if x))
     return input_formats
 
 
diff --git a/src/calibre/gui2/tools.py b/src/calibre/gui2/tools.py
index f4ee92b565..98a59ccdd5 100644
--- a/src/calibre/gui2/tools.py
+++ b/src/calibre/gui2/tools.py
@@ -88,20 +88,35 @@ def convert_single_ebook(parent, db, book_ids, auto_conversion=False, # {{{
 
                 changed = True
                 d.break_cycles()
-        except NoSupportedInputFormats:
-            bad.append(book_id)
+        except NoSupportedInputFormats as nsif:
+            bad.append((book_id, nsif.available_formats))
 
     if bad and show_no_format_warning:
-        res = []
-        for id in bad:
-            title = db.title(id, True)
-            res.append('%s'%title)
+        if len(bad) == 1 and not bad[0][1]:
+            title = db.title(bad[0][0], True)
+            warning_dialog(parent, _('Could not convert'), '<p>'+
+                _('Could not convert <b>%s</b> as it has no ebook files. If you '
+                  'think it should have files, but calibre is not finding '
+                  'them, that is most likely because you moved the book\'s '
+                  'files around outside of calibre. You will need to find those files '
+                  'and re-add them to calibre.')%title, show=True)
+        else:
+            res = []
+            for id, available_formats in bad:
+                title = db.title(id, True)
+                if available_formats:
+                    msg = _('No supported formats (Available formats: %s)')%(
+                        ', '.join(available_formats))
+                else:
+                    msg = _('This book has no actual ebook files')
+                res.append('%s - %s'%(title, msg))
 
-        msg = '%s' % '\n'.join(res)
-        warning_dialog(parent, _('Could not convert some books'),
-            _('Could not convert %(num)d of %(tot)d books, because no suitable source'
-               ' format was found.') % dict(num=len(res), tot=total),
-            msg).exec_()
+
+            msg = '%s' % '\n'.join(res)
+            warning_dialog(parent, _('Could not convert some books'),
+                _('Could not convert %(num)d of %(tot)d books, because no supported source'
+                ' formats were found.') % dict(num=len(res), tot=total),
+                msg).exec_()
 
     return jobs, changed, bad
 # }}}