diff --git a/docs/topics/auth/passwords.txt b/docs/topics/auth/passwords.txt
index 578d917cf4..aaeb929d81 100644
--- a/docs/topics/auth/passwords.txt
+++ b/docs/topics/auth/passwords.txt
@@ -232,6 +232,12 @@ follows:
    Pick a ``time_cost`` that takes an acceptable time for you.
    If ``time_cost`` set to 1 is unacceptably slow, lower ``memory_cost``.
 
+.. admonition:: ``memory_cost`` interpretation
+
+    The argon2 command-line utility and some other libraries interpret the
+    ``memory_cost`` parameter differently from the value that Django uses. The
+    conversion is given by ``memory_cost == 2 ** memory_cost_commandline``.
+
 .. _password-upgrades:
 
 Password upgrading