diff --git a/phono3py/api_phono3py.py b/phono3py/api_phono3py.py
index 7138b90a..4dc2bfbc 100644
--- a/phono3py/api_phono3py.py
+++ b/phono3py/api_phono3py.py
@@ -1225,11 +1225,11 @@ def run_phonon_solver(self, grid_points=None):
 
     def generate_displacements(
         self,
-        distance: float = 0.03,
+        distance: Optional[float] = None,
         cutoff_pair_distance: Optional[float] = None,
         is_plusminus: Union[bool, str] = "auto",
         is_diagonal: bool = True,
-        number_of_snapshots: Optional[int] = None,
+        number_of_snapshots: Optional[Union[int, Literal["auto"]]] = None,
         random_seed: Optional[int] = None,
         max_distance: Optional[float] = None,
     ):
@@ -1269,10 +1269,11 @@ def generate_displacements(
         Parameters
         ----------
         distance : float, optional
-            Constant displacement Euclidean distance. Default is 0.03. For
-            random direction and random distance displacements generation, this
-            value is also used as `min_distance`, is used to replace generated
-            random distances smaller than this value by this value.
+            Constant displacement Euclidean distance. Default is None, which
+            gives 0.03. For random direction and random distance displacements
+            generation, this value is also used as `min_distance`, is used to
+            replace generated random distances smaller than this value by this
+            value.
         cutoff_pair_distance : float, optional
             This is used as a cutoff Euclidean distance to determine if each
             pair of displacements is considered to calculate fc3 or not. Default
@@ -1288,13 +1289,14 @@ def generate_displacements(
             vectors of the supercell. With True, direction not along the basis
             vectors can be chosen when the number of the displacements may be
             reduced.
-        number_of_snapshots : int or None, optional
+        number_of_snapshots : int, "auto", or None, optional
             Number of snapshots of supercells with random displacements. Random
-            displacements are generated displacing all atoms in random
-            directions with a fixed displacement distance specified by
-            'distance' parameter, i.e., all atoms in supercell are displaced
-            with the same displacement distance in direct space. Default is
-            None.
+            displacements are generated by shifting all atoms in random
+            directions by a fixed distance specified by the `distance`
+            parameter. In other words, all atoms in the supercell are displaced
+            by the same distance in direct space. When “auto”, the minimum
+            required number of snapshots is estimated using symfc and then
+            doubled. The default is None.
         random_seed : int or None, optional
             Random seed for random displacements generation. Default is None.
         max_distance : float or None, optional
@@ -1303,11 +1305,29 @@ def generate_displacements(
             displacements generation, this value is used as `max_distance`.
 
         """
-        if number_of_snapshots is not None and number_of_snapshots > 0:
+        if distance is None:
+            _distance = 0.03
+        else:
+            _distance = distance
+
+        if number_of_snapshots is not None and (
+            number_of_snapshots == "auto" or number_of_snapshots > 0
+        ):
+            if number_of_snapshots == "auto":
+                from phonopy.interface.symfc import SymfcFCSolver
+
+                _number_of_snapshots = (
+                    SymfcFCSolver(
+                        self._supercell, self._symmetry
+                    ).estimate_numbers_of_supercells(orders=[3])[3]
+                    * 2
+                )
+            else:
+                _number_of_snapshots = number_of_snapshots
             self._dataset = self._generate_random_displacements(
-                number_of_snapshots,
+                _number_of_snapshots,
                 len(self._supercell),
-                distance=distance,
+                distance=_distance,
                 is_plusminus=is_plusminus is True,
                 random_seed=random_seed,
                 max_distance=max_distance,
@@ -1321,7 +1341,7 @@ def generate_displacements(
             )
             self._dataset = direction_to_displacement(
                 direction_dataset,
-                distance,
+                _distance,
                 self._supercell,
                 cutoff_distance=cutoff_pair_distance,
             )
@@ -1329,15 +1349,15 @@ def generate_displacements(
 
         if self._phonon_supercell_matrix is not None and self._phonon_dataset is None:
             self.generate_fc2_displacements(
-                distance=distance, is_plusminus=is_plusminus, is_diagonal=False
+                distance=_distance, is_plusminus=is_plusminus, is_diagonal=False
             )
 
     def generate_fc2_displacements(
         self,
-        distance: float = 0.03,
+        distance: Optional[float] = None,
         is_plusminus: str = "auto",
         is_diagonal: bool = False,
-        number_of_snapshots: Optional[int] = None,
+        number_of_snapshots: Optional[Union[int, Literal["auto"]]] = None,
         random_seed: Optional[int] = None,
         max_distance: Optional[float] = None,
     ):
@@ -1357,10 +1377,11 @@ def generate_fc2_displacements(
         Parameters
         ----------
         distance : float, optional
-            Constant displacement Euclidean distance. Default is 0.03. For
-            random direction and random distance displacements generation, this
-            value is also used as `min_distance`, is used to replace generated
-            random distances smaller than this value by this value.
+            Constant displacement Euclidean distance. Default is None, which
+            gives 0.03. For random direction and random distance displacements
+            generation, this value is also used as `min_distance`, is used to
+            replace generated random distances smaller than this value by this
+            value.
         is_plusminus : True, False, or 'auto', optional
             With True, atomis are displaced in both positive and negative
             directions. With False, only one direction. With 'auto', mostly
@@ -1372,13 +1393,14 @@ def generate_fc2_displacements(
             the supercell. With True, direction not along the basis vectors can
             be chosen when the number of the displacements may be reduced.
             Default is False.
-        number_of_snapshots : int or None, optional
+        number_of_snapshots : int, "auto", or None, optional
             Number of snapshots of supercells with random displacements. Random
-            displacements are generated displacing all atoms in random
-            directions with a fixed displacement distance specified by
-            'distance' parameter, i.e., all atoms in supercell are displaced
-            with the same displacement distance in direct space. Default is
-            None.
+            displacements are generated by shifting all atoms in random
+            directions by a fixed distance specified by the `distance`
+            parameter. In other words, all atoms in the supercell are displaced
+            by the same distance in direct space. When “auto”, the minimum
+            required number of snapshots is estimated using symfc and then
+            doubled. The default is None.
         random_seed : int or None, optional
             Random seed for random displacements generation. Default is None.
         max_distance : float or None, optional
@@ -1387,11 +1409,30 @@ def generate_fc2_displacements(
             displacements generation, this value is used as `max_distance`.
 
         """
-        if number_of_snapshots is not None and number_of_snapshots > 0:
+        if distance is None:
+            _distance = 0.03
+        else:
+            _distance = distance
+
+        if number_of_snapshots is not None and (
+            number_of_snapshots == "auto" or number_of_snapshots > 0
+        ):
+            if number_of_snapshots == "auto":
+                from phonopy.interface.symfc import SymfcFCSolver
+
+                _number_of_snapshots = (
+                    SymfcFCSolver(
+                        self._supercell, self._symmetry
+                    ).estimate_numbers_of_supercells(orders=[2])[2]
+                    * 2
+                )
+            else:
+                _number_of_snapshots = number_of_snapshots
+
             self._phonon_dataset = self._generate_random_displacements(
-                number_of_snapshots,
+                _number_of_snapshots,
                 len(self._phonon_supercell),
-                distance=distance,
+                distance=_distance,
                 is_plusminus=is_plusminus is True,
                 random_seed=random_seed,
                 max_distance=max_distance,
@@ -1403,7 +1444,7 @@ def generate_fc2_displacements(
                 is_diagonal=is_diagonal,
             )
             self._phonon_dataset = directions_to_displacement_dataset(
-                phonon_displacement_directions, distance, self._phonon_supercell
+                phonon_displacement_directions, _distance, self._phonon_supercell
             )
         self._phonon_supercells_with_displacements = None
 
diff --git a/phono3py/cui/create_supercells.py b/phono3py/cui/create_supercells.py
index bb0b03b8..3513caac 100644
--- a/phono3py/cui/create_supercells.py
+++ b/phono3py/cui/create_supercells.py
@@ -34,6 +34,7 @@
 # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 # POSSIBILITY OF SUCH DAMAGE.
 
+import numpy as np
 from phonopy.interface.calculator import write_supercells_with_displacements
 from phonopy.structure.cells import print_cell
 
@@ -83,10 +84,13 @@ def create_phono3py_supercells(
         random_seed=settings.random_seed,
     )
 
-    if settings.random_displacements_fc2:
+    if (
+        settings.random_displacements_fc2
+        or settings.phonon_supercell_matrix is not None
+    ):
         phono3py.generate_fc2_displacements(
             distance=distance,
-            is_plusminus=settings.is_plusminus_displacement,
+            is_plusminus=settings.is_plusminus_displacement_fc2,
             number_of_snapshots=settings.random_displacements_fc2,
             random_seed=settings.random_seed,
         )
@@ -156,4 +160,21 @@ def create_phono3py_supercells(
         if log_level:
             print("Number of displacements for special fc2: %d" % num_disps)
 
+    if log_level:
+        identity = np.eye(3, dtype=int)
+        n_pure_trans = sum(
+            [
+                (r == identity).all()
+                for r in phono3py.symmetry.symmetry_operations["rotations"]
+            ]
+        )
+
+        if len(phono3py.supercell) // len(phono3py.primitive) != n_pure_trans:
+            print("*" * 72)
+            print(
+                "Note: "
+                'A better primitive cell can be chosen by using "--pa auto" option.'
+            )
+            print("*" * 72)
+
     return phono3py
diff --git a/phono3py/cui/phono3py_argparse.py b/phono3py/cui/phono3py_argparse.py
index 8ac6400f..086bb51d 100644
--- a/phono3py/cui/phono3py_argparse.py
+++ b/phono3py/cui/phono3py_argparse.py
@@ -629,6 +629,13 @@ def get_parser(fc_symmetry=False, is_nac=False, load_phono3py_yaml=False):
         default=False,
         help="Set plus minus displacements",
     )
+    parser.add_argument(
+        "--pm-fc2",
+        dest="is_plusminus_displacements_fc2",
+        action="store_true",
+        default=False,
+        help="Set plus minus displacements for extra fc2",
+    )
     parser.add_argument(
         "--pp-unit-conversion",
         dest="pp_unit_conversion",
@@ -676,17 +683,15 @@ def get_parser(fc_symmetry=False, is_nac=False, load_phono3py_yaml=False):
         "--rd",
         "--random-displacements",
         dest="random_displacements",
-        type=int,
         default=None,
-        help="Number of supercells with random displacements",
+        help='Number of supercells with random displacements or "auto"',
     )
     parser.add_argument(
         "--rd-fc2",
         "--random-displacements-fc2",
         dest="random_displacements_fc2",
-        type=int,
         default=None,
-        help="Number of phonon supercells with random displacements",
+        help='Number of phonon supercells with random displacements or "auto"',
     )
     parser.add_argument(
         "--read-collision",
diff --git a/phono3py/cui/settings.py b/phono3py/cui/settings.py
index 096ee8d2..ffb29124 100644
--- a/phono3py/cui/settings.py
+++ b/phono3py/cui/settings.py
@@ -66,6 +66,7 @@ class Phono3pySettings(Settings):
         "is_kappa_star": True,
         "is_lbte": False,
         "is_N_U": False,
+        "is_plusminus_displacement_fc2": "auto",
         "is_real_self_energy": False,
         "is_reducible_collision_matrix": False,
         "is_spectral_function": False,
@@ -214,6 +215,10 @@ def set_is_N_U(self, val):
         """Set is_N_U."""
         self._v["is_N_U"] = val
 
+    def set_is_plusminus_displacement_fc2(self, val):
+        """Set is_plusminus_displacement_fc2."""
+        self._v["is_plusminus_displacement_fc2"] = val
+
     def set_is_real_self_energy(self, val):
         """Set is_real_self_energy."""
         self._v["is_real_self_energy"] = val
@@ -488,6 +493,10 @@ def _read_options(self):
             if self._args.is_N_U:
                 self._confs["N_U"] = ".true."
 
+        if "is_plusminus_displacements_fc2" in self._args:
+            if self._args.is_plusminus_displacements_fc2:
+                self._confs["pm_fc2"] = ".true."
+
         if "is_real_self_energy" in self._args:
             if self._args.is_real_self_energy:
                 self._confs["real_self_energy"] = ".true."
@@ -714,7 +723,6 @@ def _parse_conf(self):
                 "pinv_method",
                 "pinv_solver",
                 "num_points_in_batch",
-                "random_displacements_fc2",
                 "scattering_event_class",
             ):
                 self.set_parameter(conf_key, int(confs[conf_key]))
@@ -803,6 +811,22 @@ def _parse_conf(self):
                 else:
                     self.set_parameter("temperatures", vals)
 
+            if conf_key == "random_displacements_fc2":
+                rd = confs["random_displacements_fc2"]
+                if rd.lower() == "auto":
+                    self.set_parameter("random_displacements_fc2", "auto")
+                else:
+                    try:
+                        self.set_parameter("random_displacements_fc2", int(rd))
+                    except ValueError:
+                        self.setting_error(f"{conf_key.upper()} is incorrectly set.")
+
+            if conf_key == "pm_fc2":
+                if confs["pm_fc2"].lower() == ".false.":
+                    self.set_parameter("pm_fc2", False)
+                elif confs["pm_fc2"].lower() == ".true.":
+                    self.set_parameter("pm_fc2", True)
+
     def _set_settings(self):
         self.set_settings()
         params = self._parameters
@@ -919,6 +943,10 @@ def _set_settings(self):
         if "N_U" in params:
             self._settings.set_is_N_U(params["N_U"])
 
+        # Plus minus displacement for fc2
+        if "pm_fc2" in params:
+            self._settings.set_is_plusminus_displacement_fc2(params["pm_fc2"])
+
         # Solve reducible collision matrix but not reduced matrix
         if "reducible_collision_matrix" in params:
             self._settings.set_is_reducible_collision_matrix(
diff --git a/test/phonon3/test_displacements.py b/test/phonon3/test_displacements.py
index 91e2e1e8..b4ed0093 100644
--- a/test/phonon3/test_displacements.py
+++ b/test/phonon3/test_displacements.py
@@ -1,6 +1,11 @@
 """Tests of displacements.py."""
 
+import itertools
+from typing import Literal, Optional, Union
+
 import numpy as np
+import pytest
+from phonopy.structure.atoms import PhonopyAtoms
 
 import phono3py
 from phono3py import Phono3py
@@ -74,7 +79,49 @@
 ]
 
 
-def test_duplicates_agno2(agno2_cell):
+@pytest.mark.parametrize(
+    "is_plusminus,distance,number_of_snapshots",
+    itertools.product([False, True], [None, 0.06], [8, "auto"]),
+)
+def test_random_disps_agno2(
+    agno2_cell: PhonopyAtoms,
+    is_plusminus: bool,
+    distance: Optional[float],
+    number_of_snapshots: Union[int, Literal["auto"]],
+):
+    """Test duplicated pairs of displacements."""
+    ph3 = phono3py.load(unitcell=agno2_cell, supercell_matrix=[2, 1, 2])
+    ph3.generate_displacements(
+        number_of_snapshots=number_of_snapshots,
+        distance=distance,
+        is_plusminus=is_plusminus,
+    )
+
+    ph3.generate_fc2_displacements(
+        number_of_snapshots=number_of_snapshots,
+        distance=distance,
+        is_plusminus=is_plusminus,
+    )
+
+    for d, n_d in zip((ph3.displacements, ph3.phonon_displacements), (92, 4)):
+        if number_of_snapshots == "auto":
+            assert len(d) == n_d * (is_plusminus + 1)
+        else:
+            assert len(d) == 8 * (is_plusminus + 1)
+
+        if distance is None:
+            np.testing.assert_allclose(
+                np.linalg.norm(d, axis=2).ravel(), 0.03, atol=1e-8
+            )
+        else:
+            np.testing.assert_allclose(
+                np.linalg.norm(d, axis=2).ravel(), 0.06, atol=1e-8
+            )
+        if is_plusminus:
+            np.testing.assert_allclose(d[: len(d) // 2], -d[len(d) // 2 :], atol=1e-8)
+
+
+def test_duplicates_agno2(agno2_cell: PhonopyAtoms):
     """Test duplicated pairs of displacements."""
     ph3 = phono3py.load(unitcell=agno2_cell, supercell_matrix=[1, 1, 1])
     ph3.generate_displacements()