diff --git a/Doc/library/string.rst b/Doc/library/string.rst
index c3c0d732cf18d4..486e19ab8f9300 100644
--- a/Doc/library/string.rst
+++ b/Doc/library/string.rst
@@ -588,6 +588,13 @@ 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.  For :class:`float`, used rounding mode match the one
+for :func:`round` builtin, i.e. it should round results midway between
+representable values toward the nearest value with an even (0) least
+significant bit.  For :class:`~decimal.Decimal`, rounding mode of the current
+:ref:`context <decimal-context>` is used.
+
 
 .. _formatexamples: