diff --git a/chatmastermind/chat.py b/chatmastermind/chat.py
index 6b85ba5..366988b 100644
--- a/chatmastermind/chat.py
+++ b/chatmastermind/chat.py
@@ -129,6 +129,13 @@ class Chat:
             tags |= m.filter_tags(prefix, contain)
         return tags
 
+    def tokens(self) -> int:
+        """
+        Returns the nr. of AI language tokens used by all messages in this chat.
+        If unknown, 0 is returned.
+        """
+        return sum(m.tokens() for m in self.messages)
+
     def print(self, dump: bool = False, source_code_only: bool = False,
               with_tags: bool = False, with_file: bool = False,
               paged: bool = True) -> None:
diff --git a/chatmastermind/message.py b/chatmastermind/message.py
index 3eca26e..675ab3a 100644
--- a/chatmastermind/message.py
+++ b/chatmastermind/message.py
@@ -132,6 +132,7 @@ class Question(str):
     """
     A single question with a defined header.
     """
+    tokens: int = 0   # tokens used by this question
     txt_header: ClassVar[str] = '=== QUESTION ==='
     yaml_key: ClassVar[str] = 'question'
 
@@ -165,6 +166,7 @@ class Answer(str):
     """
     A single answer with a defined header.
     """
+    tokens: int = 0  # tokens used by this answer
     txt_header: ClassVar[str] = '=== ANSWER ==='
     yaml_key: ClassVar[str] = 'answer'
 
@@ -502,3 +504,13 @@ class Message():
 
     def as_dict(self) -> dict[str, Any]:
         return asdict(self)
+
+    def tokens(self) -> int:
+        """
+        Returns the nr. of AI language tokens used by this  message.
+        If unknown, 0 is returned.
+        """
+        if self.answer:
+            return self.question.tokens + self.answer.tokens
+        else:
+            return self.question.tokens