diff --git a/pillar/application/modules/file_storage.py b/pillar/application/modules/file_storage.py
index cc8021e6..64bcea93 100644
--- a/pillar/application/modules/file_storage.py
+++ b/pillar/application/modules/file_storage.py
@@ -628,6 +628,24 @@ def create_file_doc_for_upload(project_id, uploaded_file):
     return file_fields['_id'], internal_filename, status
 
 
+def compute_aggregate_length(file_doc, original=None):
+    """Computes the total length (in bytes) of the file and all variations.
+
+    Stores the result in file_doc['length_aggregate_in_bytes']
+    """
+
+    # Compute total size of all variations.
+    variations = file_doc.get('variations', ())
+    var_length = sum(var.get('length', 0) for var in variations)
+
+    file_doc['length_aggregate_in_bytes'] = file_doc.get('length', 0) + var_length
+
+
+def compute_aggregate_length_items(file_docs):
+    for file_doc in file_docs:
+        compute_aggregate_length(file_doc)
+
+
 def setup_app(app, url_prefix):
     app.on_pre_GET_files += on_pre_get_files
 
@@ -636,4 +654,8 @@ def setup_app(app, url_prefix):
 
     app.on_delete_item_files += before_deleting_file
 
+    app.on_update_files += compute_aggregate_length
+    app.on_replace_files += compute_aggregate_length
+    app.on_insert_files += compute_aggregate_length_items
+
     app.register_blueprint(file_storage, url_prefix=url_prefix)
diff --git a/pillar/settings.py b/pillar/settings.py
index 1a8d6837..8281b009 100644
--- a/pillar/settings.py
+++ b/pillar/settings.py
@@ -402,6 +402,10 @@ files_schema = {
         'type': 'integer',
         'required': True,
     },
+    'length_aggregate_in_bytes': {  # Size of file + all variations
+        'type': 'integer',
+        'required': False,  # it's computed on the fly anyway, so clients don't need to provide it.
+    },
     'md5': {
         'type': 'string',
         'required': True,