diff --git a/homeassistant/components/folder/sensor.py b/homeassistant/components/folder/sensor.py
index 13295d069a3..8c71208b745 100644
--- a/homeassistant/components/folder/sensor.py
+++ b/homeassistant/components/folder/sensor.py
@@ -8,8 +8,12 @@ import os
 
 import voluptuous as vol
 
-from homeassistant.components.sensor import PLATFORM_SCHEMA, SensorEntity
-from homeassistant.const import DATA_MEGABYTES
+from homeassistant.components.sensor import (
+    PLATFORM_SCHEMA,
+    SensorDeviceClass,
+    SensorEntity,
+)
+from homeassistant.const import UnitOfInformation
 from homeassistant.core import HomeAssistant
 import homeassistant.helpers.config_validation as cv
 from homeassistant.helpers.entity_platform import AddEntitiesCallback
@@ -31,14 +35,14 @@ PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend(
 )
 
 
-def get_files_list(folder_path, filter_term):
+def get_files_list(folder_path: str, filter_term: str) -> list[str]:
     """Return the list of files, applying filter."""
     query = folder_path + filter_term
     files_list = glob.glob(query)
     return files_list
 
 
-def get_size(files_list):
+def get_size(files_list: list[str]) -> int:
     """Return the sum of the size in bytes of files in the list."""
     size_list = [os.stat(f).st_size for f in files_list if os.path.isfile(f)]
     return sum(size_list)
@@ -51,7 +55,7 @@ def setup_platform(
     discovery_info: DiscoveryInfoType | None = None,
 ) -> None:
     """Set up the folder sensor."""
-    path = config[CONF_FOLDER_PATHS]
+    path: str = config[CONF_FOLDER_PATHS]
 
     if not hass.config.is_allowed_path(path):
         _LOGGER.error("Folder %s is not valid or allowed", path)
@@ -63,55 +67,28 @@ def setup_platform(
 class Folder(SensorEntity):
     """Representation of a folder."""
 
-    ICON = "mdi:folder"
+    _attr_device_class = SensorDeviceClass.DATA_SIZE
+    _attr_icon = "mdi:folder"
+    _attr_native_unit_of_measurement = UnitOfInformation.MEGABYTES
 
-    def __init__(self, folder_path, filter_term):
+    def __init__(self, folder_path: str, filter_term: str) -> None:
         """Initialize the data object."""
         folder_path = os.path.join(folder_path, "")  # If no trailing / add it
         self._folder_path = folder_path  # Need to check its a valid path
         self._filter_term = filter_term
-        self._number_of_files = None
-        self._size = None
-        self._name = os.path.split(os.path.split(folder_path)[0])[1]
-        self._unit_of_measurement = DATA_MEGABYTES
-        self._file_list = None
+        self._attr_name = os.path.split(os.path.split(folder_path)[0])[1]
 
     def update(self) -> None:
         """Update the sensor."""
         files_list = get_files_list(self._folder_path, self._filter_term)
-        self._file_list = files_list
-        self._number_of_files = len(files_list)
-        self._size = get_size(files_list)
+        number_of_files = len(files_list)
+        size = get_size(files_list)
 
-    @property
-    def name(self):
-        """Return the name of the sensor."""
-        return self._name
-
-    @property
-    def native_value(self):
-        """Return the state of the sensor."""
-        decimals = 2
-        size_mb = round(self._size / 1e6, decimals)
-        return size_mb
-
-    @property
-    def icon(self):
-        """Icon to use in the frontend, if any."""
-        return self.ICON
-
-    @property
-    def extra_state_attributes(self):
-        """Return other details about the sensor state."""
-        return {
+        self._attr_native_value = round(size / 1e6, 2)
+        self._attr_extra_state_attributes = {
             "path": self._folder_path,
             "filter": self._filter_term,
-            "number_of_files": self._number_of_files,
-            "bytes": self._size,
-            "file_list": self._file_list,
+            "number_of_files": number_of_files,
+            "bytes": size,
+            "file_list": files_list,
         }
-
-    @property
-    def native_unit_of_measurement(self):
-        """Return the unit of measurement of this entity, if any."""
-        return self._unit_of_measurement