diff --git a/Doc/library/string.rst b/Doc/library/string.rst
index 9e8e44a8abe770..a000bb49f14800 100644
--- a/Doc/library/string.rst
+++ b/Doc/library/string.rst
@@ -589,6 +589,11 @@ The available presentation types for :class:`float` and
    |         | as altered by the other format modifiers.                |
    +---------+----------------------------------------------------------+
 
+The result should be correctly rounded to a given precision ``p`` of digits
+after the decimal point.  The rounding mode for :class:`float` matches that
+of the :func:`round` builtin.  For :class:`~decimal.Decimal`, the rounding
+mode of the current :ref:`context <decimal-context>` will be used.
+
 The available presentation types for :class:`complex` are the same as those for
 :class:`float` (``'%'`` is not allowed).  Both the real and imaginary components
 of a complex number are formatted as floating-point numbers, according to the