diff --git a/Doc/c-api/conversion.rst b/Doc/c-api/conversion.rst
index 52fe197..403c183 100644
--- a/Doc/c-api/conversion.rst
+++ b/Doc/c-api/conversion.rst
@@ -62,6 +62,43 @@
 
    See the Unix man page :manpage:`strtod(2)` for details.
 
+   .. deprecated:: 3.1
+      Use :cfunc:`PyOS_string_to_double` instead.
+
+
+.. cfunction:: double PyOS_string_to_double(const char *s, char **endptr, PyObject *overflow_exception)
+
+   Convert a string ``s`` to a :ctype:`double`, raising a Python
+   exception on failure.  The set of accepted strings corresponds to
+   the set of strings accepted by Python's :func:`float` constructor,
+   except that ``s`` must not have leading or trailing whitespace.
+   The conversion is independent of the current locale.
+
+   If ``endptr`` is ``NULL``, convert the whole string.  Raise
+   ValueError and return ``-1.0`` if the string is not a valid
+   representation of a floating-point number.
+
+   If endptr is not ``NULL``, convert as much of the string as
+   possible and set ``*endptr`` to point to the first unconverted
+   character.  If no initial segment of the string is the valid
+   representation of a floating-point number, set ``*endptr`` to point
+   to the beginning of the string, raise ValueError, and return
+   ``-1.0``.
+
+   If ``s`` represents a value that is too large to store in a float
+   (for example, ``"1e500"`` is such a string on many platforms) then
+   if ``overflow_exception`` is ``NULL`` return ``Py_HUGE_VAL`` (with
+   an appropriate sign) and don't set any exception.  Otherwise,
+   ``overflow_exception`` must point to a Python exception object;
+   raise that exception and return ``-1.0``.  In both cases, set
+   ``*endptr`` to point to the first character after the converted value.
+
+   If any other error occurs during the conversion (for example an
+   out-of-memory error), set the appropriate Python exception and
+   return ``-1.0``.
+
+   .. versionadded:: 3.1
+
 
 .. cfunction:: char* PyOS_ascii_formatd(char *buffer, size_t buf_len, const char *format, double d)
 
@@ -117,6 +154,9 @@
 
    See the Unix man page :manpage:`atof(2)` for details.
 
+   .. deprecated:: 3.1
+      Use PyOS_string_to_double instead.
+
 
 .. cfunction:: char* PyOS_stricmp(char *s1, char *s2)