diff --git a/reviewboard/diffviewer/management/commands/condensediffs.py b/reviewboard/diffviewer/management/commands/condensediffs.py
index bd8082dbeb1bb2b66771a99e15effb6bdb64fda0..a0d6571c566acc2c7ca75498608921670c16ce57 100644
--- a/reviewboard/diffviewer/management/commands/condensediffs.py
+++ b/reviewboard/diffviewer/management/commands/condensediffs.py
@@ -48,7 +48,8 @@ class Command(NoArgsCommand):
             'Condensed stored diffs from %s bytes to %s bytes '
             '(%d%% savings)\n'
             % (intcomma(old_diff_size), intcomma(new_diff_size),
-               float(new_diff_size) / float(old_diff_size) * 100.0))
+               (float(old_diff_size - new_diff_size) /
+                float(old_diff_size) * 100.0)))
 
     def _on_processed_filediff(self, filediff):
         self.i += 1
diff --git a/reviewboard/diffviewer/managers.py b/reviewboard/diffviewer/managers.py
index 1456da76d41cd42848dd50458fa82fd6a04a99de..b18df927208101db0e03dee13b4bf73559915ddf 100644
--- a/reviewboard/diffviewer/managers.py
+++ b/reviewboard/diffviewer/managers.py
@@ -54,8 +54,8 @@ class FileDiffManager(models.Manager):
             for filediff in unmigrated_filediffs[:OBJECT_LIMIT].iterator():
                 total_diffs_migrated += 1
 
-                diff_size = len(filediff.diff64)
-                parent_diff_size = len(filediff.parent_diff64)
+                diff_size = len(filediff.get_diff64_base64())
+                parent_diff_size = len(filediff.get_parent_diff64_base64())
 
                 total_diff_size += diff_size + parent_diff_size