diff --git a/tools/uncompressedsize.py b/tools/uncompressedsize.py
index 32ba0957c..f326c4d3d 100644
--- a/tools/uncompressedsize.py
+++ b/tools/uncompressedsize.py
@@ -5,12 +5,14 @@ from data import model
 from data.database import ImageStorage
 from app import app, storage as store
 from data.database import db
+from gzip import GzipFile
+from StringIO import StringIO
 
 
 logger = logging.getLogger(__name__)
 
 
-def backfill_sizes():
+def backfill_sizes_from_json():
   query = (ImageStorage
            .select()
            .where(ImageStorage.uncompressed_size == None, ImageStorage.uploading == False)
@@ -47,8 +49,57 @@ def backfill_sizes():
         image_storage.save()
 
 
+def backfill_sizes_from_data():
+  storage_ids = list(ImageStorage
+           .select(ImageStorage.uuid)
+           .where(ImageStorage.uncompressed_size == -1, ImageStorage.uploading == False))
+
+  counter = 0
+  for uuid in [s.uuid for s in storage_ids]:
+    counter += 1
+
+    # Load the storage with locations.
+    logger.debug('Loading entry: %s (%s/%s)', uuid, counter, len(storage_ids))
+    with_locations = model.get_storage_by_uuid(uuid)
+    layer_size = -2
+
+    # Read the layer from backing storage.
+    logger.debug('Reading entry: %s (%s bytes)', uuid, with_locations.image_size)
+    try:
+      layer_data = store.get_content(with_locations.locations, store.image_layer_path(uuid))
+    except Exception as ex:
+      logger.debug('Could not read entry: %s. Reason: %s', uuid, ex)
+      continue
+
+    # Calculate the uncompressed size. 
+    try:
+      layer_stream = StringIO(layer_data)
+      with GzipFile(fileobj=layer_stream, mode='rb') as gzip_file:
+        layer_size = len(gzip_file.read())
+        logger.debug('%s' % gzip_file.size)
+
+      layer_stream.close()
+    except Exception as ex:
+      logger.debug('Could not gunzip entry: %s. Reason: %s', uuid, ex)
+      continue
+    
+    # Write the size to the image storage. We do so under a transaction AFTER checking to
+    # make sure the image storage still exists and has not changed.
+    logger.debug('Writing entry: %s. Size: %s', uuid, layer_size)
+    with app.config['DB_TRANSACTION_FACTORY'](db):
+      try:  
+        current_record = model.get_storage_by_uuid(uuid)
+      except:
+        # Record no longer exists.
+        continue
+
+      if not current_record.uploading and current_record.uncompressed_size == -1:
+        current_record.uncompressed_size = layer_size
+        current_record.save()
+
+
 if __name__ == "__main__":
   logging.basicConfig(level=logging.DEBUG)
   logging.getLogger('boto').setLevel(logging.CRITICAL)
 
-  backfill_sizes()
+  backfill_sizes_from_data()