diff --git a/lms/djangoapps/courseware/courses.py b/lms/djangoapps/courseware/courses.py
index 62bd6bf5c982..5dc4a7ce9107 100644
--- a/lms/djangoapps/courseware/courses.py
+++ b/lms/djangoapps/courseware/courses.py
@@ -795,10 +795,11 @@ def get_assignments_grades(user, course_id, cache_timeout):
             collected_block_structure = get_block_structure_manager(course_id).get_collected()
 
             total_bytes_in_one_mb = 1024 * 1024
-            data_size_in_mbs = round(len(pickle.dumps(collected_block_structure)) / total_bytes_in_one_mb, 2)
-            if data_size_in_mbs < total_bytes_in_one_mb * 2:
+            data_size_in_bytes = len(pickle.dumps(collected_block_structure))
+            if data_size_in_bytes < total_bytes_in_one_mb * 2:
                 cache.set(cache_key, collected_block_structure, cache_timeout)
             else:
+                data_size_in_mbs = round(data_size_in_bytes / total_bytes_in_one_mb, 2)
                 # .. custom_attribute_name: collected_block_structure_size_in_mbs
                 # .. custom_attribute_description: contains the data chunk size in MBs. The size on which
                 #   the memcached client failed to store value in cache.
diff --git a/openedx/core/djangoapps/content/block_structure/store.py b/openedx/core/djangoapps/content/block_structure/store.py
index 409dae988e92..bb6359b9d3a3 100644
--- a/openedx/core/djangoapps/content/block_structure/store.py
+++ b/openedx/core/djangoapps/content/block_structure/store.py
@@ -137,8 +137,9 @@ def _add_to_cache(self, serialized_data, bs_model):
         """
         cache_key = self._encode_root_cache_key(bs_model)
         total_bytes_in_one_mb = 1024 * 1024
-        data_size_in_mbs = round(len(serialized_data) / total_bytes_in_one_mb, 2)
-        if data_size_in_mbs < total_bytes_in_one_mb * 2:
+        data_size_in_bytes = len(serialized_data)
+        data_size_in_mbs = round(data_size_in_bytes / total_bytes_in_one_mb, 2)
+        if data_size_in_bytes < total_bytes_in_one_mb * 2:
             self._cache.set(cache_key, serialized_data, timeout=config.cache_timeout_in_seconds())
             logger.info("BlockStructure: Added to cache; %s, size: %.2fMB", bs_model, data_size_in_mbs)
         else: