diff --git a/aider/repomap.py b/aider/repomap.py
index e1fd15b69..51a850ef3 100644
--- a/aider/repomap.py
+++ b/aider/repomap.py
@@ -395,13 +395,21 @@ class RepoMap:
 
         chat_rel_fnames = [self.get_rel_fname(fname) for fname in chat_fnames]
 
-        dump(max_map_tokens)
-
-        # Guess a small starting number to help with giant repos
-        middle = min(max_map_tokens // 50, num_tags)
-
         self.tree_cache = dict()
 
+        # Estimate initial middle value
+        sample_size = min(100, num_tags)
+        sample_tree = self.to_tree(ranked_tags[:sample_size], chat_rel_fnames)
+        sample_tokens = self.token_count(sample_tree)
+        
+        if sample_tokens > 0:
+            estimated_tags = int((max_map_tokens / sample_tokens) * sample_size)
+            middle = min(estimated_tags, num_tags)
+        else:
+            middle = min(max_map_tokens // 50, num_tags)
+
+        dump(max_map_tokens, sample_size, sample_tokens, estimated_tags, middle)
+
         while lower_bound <= upper_bound:
             dump(lower_bound, middle, upper_bound)