diff --git a/homeassistant/components/sensor/__init__.py b/homeassistant/components/sensor/__init__.py
index 7beac83f059911..067adb128170a2 100644
--- a/homeassistant/components/sensor/__init__.py
+++ b/homeassistant/components/sensor/__init__.py
@@ -11,13 +11,8 @@
 from math import floor, log10
 from typing import Any, Final, cast, final
 
-import voluptuous as vol
-
-from homeassistant.backports.enum import StrEnum
 from homeassistant.config_entries import ConfigEntry
 from homeassistant.const import (  # noqa: F401, pylint: disable=[hass-deprecated-import]
-    CONCENTRATION_MICROGRAMS_PER_CUBIC_METER,
-    CONCENTRATION_PARTS_PER_MILLION,
     CONF_UNIT_OF_MEASUREMENT,
     DEVICE_CLASS_AQI,
     DEVICE_CLASS_BATTERY,
@@ -47,34 +42,11 @@
     DEVICE_CLASS_TIMESTAMP,
     DEVICE_CLASS_VOLATILE_ORGANIC_COMPOUNDS,
     DEVICE_CLASS_VOLTAGE,
-    LIGHT_LUX,
-    PERCENTAGE,
-    POWER_VOLT_AMPERE_REACTIVE,
-    SIGNAL_STRENGTH_DECIBELS,
-    SIGNAL_STRENGTH_DECIBELS_MILLIWATT,
-    UnitOfApparentPower,
-    UnitOfDataRate,
-    UnitOfElectricCurrent,
-    UnitOfElectricPotential,
-    UnitOfEnergy,
-    UnitOfFrequency,
-    UnitOfInformation,
-    UnitOfIrradiance,
-    UnitOfLength,
-    UnitOfMass,
-    UnitOfPower,
-    UnitOfPrecipitationDepth,
-    UnitOfPressure,
-    UnitOfSoundPressure,
-    UnitOfSpeed,
     UnitOfTemperature,
-    UnitOfTime,
-    UnitOfVolume,
-    UnitOfVolumetricFlux,
 )
 from homeassistant.core import HomeAssistant, callback
 from homeassistant.helpers import entity_registry as er
-from homeassistant.helpers.config_validation import (  # noqa: F401
+from homeassistant.helpers.config_validation import (
     PLATFORM_SCHEMA,
     PLATFORM_SCHEMA_BASE,
 )
@@ -84,475 +56,47 @@
 from homeassistant.helpers.restore_state import ExtraStoredData, RestoreEntity
 from homeassistant.helpers.typing import ConfigType, StateType
 from homeassistant.util import dt as dt_util
-from homeassistant.util.unit_conversion import (
-    BaseUnitConverter,
-    DataRateConverter,
-    DistanceConverter,
-    ElectricCurrentConverter,
-    ElectricPotentialConverter,
-    InformationConverter,
-    MassConverter,
-    PressureConverter,
-    SpeedConverter,
-    TemperatureConverter,
-    VolumeConverter,
-)
 
-from .const import CONF_STATE_CLASS  # noqa: F401
+from .const import (  # noqa: F401
+    ATTR_LAST_RESET,
+    ATTR_OPTIONS,
+    ATTR_STATE_CLASS,
+    CONF_STATE_CLASS,
+    DEVICE_CLASS_UNITS,
+    DEVICE_CLASSES,
+    DEVICE_CLASSES_SCHEMA,
+    DOMAIN,
+    STATE_CLASS_MEASUREMENT,
+    STATE_CLASS_TOTAL,
+    STATE_CLASS_TOTAL_INCREASING,
+    STATE_CLASSES,
+    STATE_CLASSES_SCHEMA,
+    UNIT_CONVERTERS,
+    SensorDeviceClass,
+    SensorStateClass,
+)
 
 _LOGGER: Final = logging.getLogger(__name__)
 
-ATTR_LAST_RESET: Final = "last_reset"
-ATTR_STATE_CLASS: Final = "state_class"
-ATTR_OPTIONS: Final = "options"
-
-DOMAIN: Final = "sensor"
-
 ENTITY_ID_FORMAT: Final = DOMAIN + ".{}"
 
 SCAN_INTERVAL: Final = timedelta(seconds=30)
 
-
-class SensorDeviceClass(StrEnum):
-    """Device class for sensors."""
-
-    # Non-numerical device classes
-    DATE = "date"
-    """Date.
-
-    Unit of measurement: `None`
-
-    ISO8601 format: https://en.wikipedia.org/wiki/ISO_8601
-    """
-
-    DURATION = "duration"
-    """Fixed duration.
-
-    Unit of measurement: `d`, `h`, `min`, `s`
-    """
-
-    ENUM = "enum"
-    """Enumeration.
-
-    Provides a fixed list of options the state of the sensor can be in.
-
-    Unit of measurement: `None`
-    """
-
-    TIMESTAMP = "timestamp"
-    """Timestamp.
-
-    Unit of measurement: `None`
-
-    ISO8601 format: https://en.wikipedia.org/wiki/ISO_8601
-    """
-
-    # Numerical device classes, these should be aligned with NumberDeviceClass
-    APPARENT_POWER = "apparent_power"
-    """Apparent power.
-
-    Unit of measurement: `VA`
-    """
-
-    AQI = "aqi"
-    """Air Quality Index.
-
-    Unit of measurement: `None`
-    """
-
-    ATMOSPHERIC_PRESSURE = "atmospheric_pressure"
-    """Atmospheric pressure.
-
-    Unit of measurement: `UnitOfPressure` units
-    """
-
-    BATTERY = "battery"
-    """Percentage of battery that is left.
-
-    Unit of measurement: `%`
-    """
-
-    CO = "carbon_monoxide"
-    """Carbon Monoxide gas concentration.
-
-    Unit of measurement: `ppm` (parts per million)
-    """
-
-    CO2 = "carbon_dioxide"
-    """Carbon Dioxide gas concentration.
-
-    Unit of measurement: `ppm` (parts per million)
-    """
-
-    CURRENT = "current"
-    """Current.
-
-    Unit of measurement: `A`, `mA`
-    """
-
-    DATA_RATE = "data_rate"
-    """Data rate.
-
-    Unit of measurement: UnitOfDataRate
-    """
-
-    DATA_SIZE = "data_size"
-    """Data size.
-
-    Unit of measurement: UnitOfInformation
-    """
-
-    DISTANCE = "distance"
-    """Generic distance.
-
-    Unit of measurement: `LENGTH_*` units
-    - SI /metric: `mm`, `cm`, `m`, `km`
-    - USCS / imperial: `in`, `ft`, `yd`, `mi`
-    """
-
-    ENERGY = "energy"
-    """Energy.
-
-    Unit of measurement: `Wh`, `kWh`, `MWh`, `GJ`
-    """
-
-    FREQUENCY = "frequency"
-    """Frequency.
-
-    Unit of measurement: `Hz`, `kHz`, `MHz`, `GHz`
-    """
-
-    GAS = "gas"
-    """Gas.
-
-    Unit of measurement:
-    - SI / metric: `m³`
-    - USCS / imperial: `ft³`, `CCF`
-    """
-
-    HUMIDITY = "humidity"
-    """Relative humidity.
-
-    Unit of measurement: `%`
-    """
-
-    ILLUMINANCE = "illuminance"
-    """Illuminance.
-
-    Unit of measurement: `lx`
-    """
-
-    IRRADIANCE = "irradiance"
-    """Irradiance.
-
-    Unit of measurement:
-    - SI / metric: `W/m²`
-    - USCS / imperial: `BTU/(h⋅ft²)`
-    """
-
-    MOISTURE = "moisture"
-    """Moisture.
-
-    Unit of measurement: `%`
-    """
-
-    MONETARY = "monetary"
-    """Amount of money.
-
-    Unit of measurement: ISO4217 currency code
-
-    See https://en.wikipedia.org/wiki/ISO_4217#Active_codes for active codes
-    """
-
-    NITROGEN_DIOXIDE = "nitrogen_dioxide"
-    """Amount of NO2.
-
-    Unit of measurement: `µg/m³`
-    """
-
-    NITROGEN_MONOXIDE = "nitrogen_monoxide"
-    """Amount of NO.
-
-    Unit of measurement: `µg/m³`
-    """
-
-    NITROUS_OXIDE = "nitrous_oxide"
-    """Amount of N2O.
-
-    Unit of measurement: `µg/m³`
-    """
-
-    OZONE = "ozone"
-    """Amount of O3.
-
-    Unit of measurement: `µg/m³`
-    """
-
-    PM1 = "pm1"
-    """Particulate matter <= 0.1 μm.
-
-    Unit of measurement: `µg/m³`
-    """
-
-    PM10 = "pm10"
-    """Particulate matter <= 10 μm.
-
-    Unit of measurement: `µg/m³`
-    """
-
-    PM25 = "pm25"
-    """Particulate matter <= 2.5 μm.
-
-    Unit of measurement: `µg/m³`
-    """
-
-    POWER_FACTOR = "power_factor"
-    """Power factor.
-
-    Unit of measurement: `%`
-    """
-
-    POWER = "power"
-    """Power.
-
-    Unit of measurement: `W`, `kW`
-    """
-
-    PRECIPITATION = "precipitation"
-    """Precipitation.
-
-    Unit of measurement: UnitOfPrecipitationDepth
-    - SI / metric: `cm`, `mm`
-    - USCS / imperial: `in`
-    """
-
-    PRECIPITATION_INTENSITY = "precipitation_intensity"
-    """Precipitation intensity.
-
-    Unit of measurement: UnitOfVolumetricFlux
-    - SI /metric: `mm/d`, `mm/h`
-    - USCS / imperial: `in/d`, `in/h`
-    """
-
-    PRESSURE = "pressure"
-    """Pressure.
-
-    Unit of measurement:
-    - `mbar`, `cbar`, `bar`
-    - `Pa`, `hPa`, `kPa`
-    - `inHg`
-    - `psi`
-    """
-
-    REACTIVE_POWER = "reactive_power"
-    """Reactive power.
-
-    Unit of measurement: `var`
-    """
-
-    SIGNAL_STRENGTH = "signal_strength"
-    """Signal strength.
-
-    Unit of measurement: `dB`, `dBm`
-    """
-
-    SOUND_PRESSURE = "sound_pressure"
-    """Sound pressure.
-
-    Unit of measurement: `dB`, `dBA`
-    """
-
-    SPEED = "speed"
-    """Generic speed.
-
-    Unit of measurement: `SPEED_*` units or `UnitOfVolumetricFlux`
-    - SI /metric: `mm/d`, `mm/h`, `m/s`, `km/h`
-    - USCS / imperial: `in/d`, `in/h`, `ft/s`, `mph`
-    - Nautical: `kn`
-    """
-
-    SULPHUR_DIOXIDE = "sulphur_dioxide"
-    """Amount of SO2.
-
-    Unit of measurement: `µg/m³`
-    """
-
-    TEMPERATURE = "temperature"
-    """Temperature.
-
-    Unit of measurement: `°C`, `°F`
-    """
-
-    VOLATILE_ORGANIC_COMPOUNDS = "volatile_organic_compounds"
-    """Amount of VOC.
-
-    Unit of measurement: `µg/m³`
-    """
-
-    VOLTAGE = "voltage"
-    """Voltage.
-
-    Unit of measurement: `V`, `mV`
-    """
-
-    VOLUME = "volume"
-    """Generic volume.
-
-    Unit of measurement: `VOLUME_*` units
-    - SI / metric: `mL`, `L`, `m³`
-    - USCS / imperial: `ft³`, `CCF`, `fl. oz.`, `gal` (warning: volumes expressed in
-    USCS/imperial units are currently assumed to be US volumes)
-    """
-
-    WATER = "water"
-    """Water.
-
-    Unit of measurement:
-    - SI / metric: `m³`, `L`
-    - USCS / imperial: `ft³`, `CCF`, `gal` (warning: volumes expressed in
-    USCS/imperial units are currently assumed to be US volumes)
-    """
-
-    WEIGHT = "weight"
-    """Generic weight, represents a measurement of an object's mass.
-
-    Weight is used instead of mass to fit with every day language.
-
-    Unit of measurement: `MASS_*` units
-    - SI / metric: `µg`, `mg`, `g`, `kg`
-    - USCS / imperial: `oz`, `lb`
-    """
-
-    WIND_SPEED = "wind_speed"
-    """Wind speed.
-
-    Unit of measurement: `SPEED_*` units
-    - SI /metric: `m/s`, `km/h`
-    - USCS / imperial: `ft/s`, `mph`
-    - Nautical: `kn`
-    """
-
-
-DEVICE_CLASSES_SCHEMA: Final = vol.All(vol.Lower, vol.Coerce(SensorDeviceClass))
-
-# DEVICE_CLASSES is deprecated as of 2021.12
-# use the SensorDeviceClass enum instead.
-DEVICE_CLASSES: Final[list[str]] = [cls.value for cls in SensorDeviceClass]
-
-
-class SensorStateClass(StrEnum):
-    """State class for sensors."""
-
-    MEASUREMENT = "measurement"
-    """The state represents a measurement in present time."""
-
-    TOTAL = "total"
-    """The state represents a total amount.
-
-    For example: net energy consumption"""
-
-    TOTAL_INCREASING = "total_increasing"
-    """The state represents a monotonically increasing total.
-
-    For example: an amount of consumed gas"""
-
-
-STATE_CLASSES_SCHEMA: Final = vol.All(vol.Lower, vol.Coerce(SensorStateClass))
-
-
-# STATE_CLASS* is deprecated as of 2021.12
-# use the SensorStateClass enum instead.
-STATE_CLASS_MEASUREMENT: Final = "measurement"
-STATE_CLASS_TOTAL: Final = "total"
-STATE_CLASS_TOTAL_INCREASING: Final = "total_increasing"
-STATE_CLASSES: Final[list[str]] = [cls.value for cls in SensorStateClass]
-
-# Note: this needs to be aligned with frontend: OVERRIDE_SENSOR_UNITS in
-# `entity-registry-settings.ts`
-UNIT_CONVERTERS: dict[SensorDeviceClass | str | None, type[BaseUnitConverter]] = {
-    SensorDeviceClass.DATA_RATE: DataRateConverter,
-    SensorDeviceClass.DATA_SIZE: InformationConverter,
-    SensorDeviceClass.DISTANCE: DistanceConverter,
-    SensorDeviceClass.CURRENT: ElectricCurrentConverter,
-    SensorDeviceClass.GAS: VolumeConverter,
-    SensorDeviceClass.PRECIPITATION: DistanceConverter,
-    SensorDeviceClass.PRESSURE: PressureConverter,
-    SensorDeviceClass.SPEED: SpeedConverter,
-    SensorDeviceClass.TEMPERATURE: TemperatureConverter,
-    SensorDeviceClass.VOLTAGE: ElectricPotentialConverter,
-    SensorDeviceClass.VOLUME: VolumeConverter,
-    SensorDeviceClass.WATER: VolumeConverter,
-    SensorDeviceClass.WEIGHT: MassConverter,
-    SensorDeviceClass.WIND_SPEED: SpeedConverter,
-}
-
-DEVICE_CLASS_UNITS: dict[SensorDeviceClass, set[type[StrEnum] | str | None]] = {
-    SensorDeviceClass.APPARENT_POWER: set(UnitOfApparentPower),
-    SensorDeviceClass.AQI: {None},
-    SensorDeviceClass.ATMOSPHERIC_PRESSURE: set(UnitOfPressure),
-    SensorDeviceClass.BATTERY: {PERCENTAGE},
-    SensorDeviceClass.CO: {CONCENTRATION_PARTS_PER_MILLION},
-    SensorDeviceClass.CO2: {CONCENTRATION_PARTS_PER_MILLION},
-    SensorDeviceClass.CURRENT: set(UnitOfElectricCurrent),
-    SensorDeviceClass.DATA_RATE: set(UnitOfDataRate),
-    SensorDeviceClass.DATA_SIZE: set(UnitOfInformation),
-    SensorDeviceClass.DISTANCE: set(UnitOfLength),
-    SensorDeviceClass.DURATION: {
-        UnitOfTime.DAYS,
-        UnitOfTime.HOURS,
-        UnitOfTime.MINUTES,
-        UnitOfTime.SECONDS,
-    },
-    SensorDeviceClass.ENERGY: set(UnitOfEnergy),
-    SensorDeviceClass.FREQUENCY: set(UnitOfFrequency),
-    SensorDeviceClass.GAS: {
-        UnitOfVolume.CENTUM_CUBIC_FEET,
-        UnitOfVolume.CUBIC_FEET,
-        UnitOfVolume.CUBIC_METERS,
-    },
-    SensorDeviceClass.HUMIDITY: {PERCENTAGE},
-    SensorDeviceClass.ILLUMINANCE: {LIGHT_LUX},
-    SensorDeviceClass.IRRADIANCE: set(UnitOfIrradiance),
-    SensorDeviceClass.MOISTURE: {PERCENTAGE},
-    SensorDeviceClass.NITROGEN_DIOXIDE: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
-    SensorDeviceClass.NITROGEN_MONOXIDE: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
-    SensorDeviceClass.NITROUS_OXIDE: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
-    SensorDeviceClass.OZONE: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
-    SensorDeviceClass.PM1: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
-    SensorDeviceClass.PM10: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
-    SensorDeviceClass.PM25: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
-    SensorDeviceClass.POWER_FACTOR: {PERCENTAGE},
-    SensorDeviceClass.POWER: {UnitOfPower.WATT, UnitOfPower.KILO_WATT},
-    SensorDeviceClass.PRECIPITATION: set(UnitOfPrecipitationDepth),
-    SensorDeviceClass.PRECIPITATION_INTENSITY: set(UnitOfVolumetricFlux),
-    SensorDeviceClass.PRESSURE: set(UnitOfPressure),
-    SensorDeviceClass.REACTIVE_POWER: {POWER_VOLT_AMPERE_REACTIVE},
-    SensorDeviceClass.SIGNAL_STRENGTH: {
-        SIGNAL_STRENGTH_DECIBELS,
-        SIGNAL_STRENGTH_DECIBELS_MILLIWATT,
-    },
-    SensorDeviceClass.SOUND_PRESSURE: set(UnitOfSoundPressure),
-    SensorDeviceClass.SPEED: set(UnitOfSpeed).union(set(UnitOfVolumetricFlux)),
-    SensorDeviceClass.SULPHUR_DIOXIDE: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
-    SensorDeviceClass.TEMPERATURE: {
-        UnitOfTemperature.CELSIUS,
-        UnitOfTemperature.FAHRENHEIT,
-    },
-    SensorDeviceClass.VOLATILE_ORGANIC_COMPOUNDS: {
-        CONCENTRATION_MICROGRAMS_PER_CUBIC_METER
-    },
-    SensorDeviceClass.VOLTAGE: set(UnitOfElectricPotential),
-    SensorDeviceClass.VOLUME: set(UnitOfVolume),
-    SensorDeviceClass.WATER: {
-        UnitOfVolume.CENTUM_CUBIC_FEET,
-        UnitOfVolume.CUBIC_FEET,
-        UnitOfVolume.CUBIC_METERS,
-        UnitOfVolume.GALLONS,
-        UnitOfVolume.LITERS,
-    },
-    SensorDeviceClass.WEIGHT: set(UnitOfMass),
-    SensorDeviceClass.WIND_SPEED: set(UnitOfSpeed),
-}
+__all__ = [
+    "ATTR_LAST_RESET",
+    "ATTR_OPTIONS",
+    "ATTR_STATE_CLASS",
+    "CONF_STATE_CLASS",
+    "DOMAIN",
+    "PLATFORM_SCHEMA_BASE",
+    "PLATFORM_SCHEMA",
+    "RestoreSensor",
+    "SensorDeviceClass",
+    "SensorEntity",
+    "SensorEntityDescription",
+    "SensorExtraStoredData",
+    "SensorStateClass",
+]
 
 # mypy: disallow-any-generics
 
@@ -837,7 +381,7 @@ def unit_of_measurement(self) -> str | None:
         native_unit_of_measurement = self.native_unit_of_measurement
 
         if (
-            self.device_class == DEVICE_CLASS_TEMPERATURE
+            self.device_class == SensorDeviceClass.TEMPERATURE
             and native_unit_of_measurement
             in {UnitOfTemperature.CELSIUS, UnitOfTemperature.FAHRENHEIT}
         ):
@@ -856,7 +400,7 @@ def state(self) -> Any:
         device_class = self.device_class
 
         # Received a datetime
-        if value is not None and device_class == DEVICE_CLASS_TIMESTAMP:
+        if value is not None and device_class == SensorDeviceClass.TIMESTAMP:
             try:
                 # We cast the value, to avoid using isinstance, but satisfy
                 # typechecking. The errors are guarded in this try.
@@ -878,7 +422,7 @@ def state(self) -> Any:
                 ) from err
 
         # Received a date value
-        if value is not None and device_class == DEVICE_CLASS_DATE:
+        if value is not None and device_class == SensorDeviceClass.DATE:
             try:
                 # We cast the value, to avoid using isinstance, but satisfy
                 # typechecking. The errors are guarded in this try.
diff --git a/homeassistant/components/sensor/const.py b/homeassistant/components/sensor/const.py
index 54d683242ea10c..239cb36cf6e605 100644
--- a/homeassistant/components/sensor/const.py
+++ b/homeassistant/components/sensor/const.py
@@ -1,4 +1,499 @@
 """Constants for sensor."""
+from __future__ import annotations
+
 from typing import Final
 
+import voluptuous as vol
+
+from homeassistant.backports.enum import StrEnum
+from homeassistant.const import (
+    CONCENTRATION_MICROGRAMS_PER_CUBIC_METER,
+    CONCENTRATION_PARTS_PER_MILLION,
+    LIGHT_LUX,
+    PERCENTAGE,
+    POWER_VOLT_AMPERE_REACTIVE,
+    SIGNAL_STRENGTH_DECIBELS,
+    SIGNAL_STRENGTH_DECIBELS_MILLIWATT,
+    UnitOfApparentPower,
+    UnitOfDataRate,
+    UnitOfElectricCurrent,
+    UnitOfElectricPotential,
+    UnitOfEnergy,
+    UnitOfFrequency,
+    UnitOfInformation,
+    UnitOfIrradiance,
+    UnitOfLength,
+    UnitOfMass,
+    UnitOfPower,
+    UnitOfPrecipitationDepth,
+    UnitOfPressure,
+    UnitOfSoundPressure,
+    UnitOfSpeed,
+    UnitOfTemperature,
+    UnitOfTime,
+    UnitOfVolume,
+    UnitOfVolumetricFlux,
+)
+from homeassistant.util.unit_conversion import (
+    BaseUnitConverter,
+    DataRateConverter,
+    DistanceConverter,
+    ElectricCurrentConverter,
+    ElectricPotentialConverter,
+    InformationConverter,
+    MassConverter,
+    PressureConverter,
+    SpeedConverter,
+    TemperatureConverter,
+    VolumeConverter,
+)
+
+DOMAIN: Final = "sensor"
+
 CONF_STATE_CLASS: Final = "state_class"
+
+ATTR_LAST_RESET: Final = "last_reset"
+ATTR_STATE_CLASS: Final = "state_class"
+ATTR_OPTIONS: Final = "options"
+
+
+class SensorDeviceClass(StrEnum):
+    """Device class for sensors."""
+
+    # Non-numerical device classes
+    DATE = "date"
+    """Date.
+
+    Unit of measurement: `None`
+
+    ISO8601 format: https://en.wikipedia.org/wiki/ISO_8601
+    """
+
+    DURATION = "duration"
+    """Fixed duration.
+
+    Unit of measurement: `d`, `h`, `min`, `s`
+    """
+
+    ENUM = "enum"
+    """Enumeration.
+
+    Provides a fixed list of options the state of the sensor can be in.
+
+    Unit of measurement: `None`
+    """
+
+    TIMESTAMP = "timestamp"
+    """Timestamp.
+
+    Unit of measurement: `None`
+
+    ISO8601 format: https://en.wikipedia.org/wiki/ISO_8601
+    """
+
+    # Numerical device classes, these should be aligned with NumberDeviceClass
+    APPARENT_POWER = "apparent_power"
+    """Apparent power.
+
+    Unit of measurement: `VA`
+    """
+
+    AQI = "aqi"
+    """Air Quality Index.
+
+    Unit of measurement: `None`
+    """
+
+    ATMOSPHERIC_PRESSURE = "atmospheric_pressure"
+    """Atmospheric pressure.
+
+    Unit of measurement: `UnitOfPressure` units
+    """
+
+    BATTERY = "battery"
+    """Percentage of battery that is left.
+
+    Unit of measurement: `%`
+    """
+
+    CO = "carbon_monoxide"
+    """Carbon Monoxide gas concentration.
+
+    Unit of measurement: `ppm` (parts per million)
+    """
+
+    CO2 = "carbon_dioxide"
+    """Carbon Dioxide gas concentration.
+
+    Unit of measurement: `ppm` (parts per million)
+    """
+
+    CURRENT = "current"
+    """Current.
+
+    Unit of measurement: `A`, `mA`
+    """
+
+    DATA_RATE = "data_rate"
+    """Data rate.
+
+    Unit of measurement: UnitOfDataRate
+    """
+
+    DATA_SIZE = "data_size"
+    """Data size.
+
+    Unit of measurement: UnitOfInformation
+    """
+
+    DISTANCE = "distance"
+    """Generic distance.
+
+    Unit of measurement: `LENGTH_*` units
+    - SI /metric: `mm`, `cm`, `m`, `km`
+    - USCS / imperial: `in`, `ft`, `yd`, `mi`
+    """
+
+    ENERGY = "energy"
+    """Energy.
+
+    Unit of measurement: `Wh`, `kWh`, `MWh`, `GJ`
+    """
+
+    FREQUENCY = "frequency"
+    """Frequency.
+
+    Unit of measurement: `Hz`, `kHz`, `MHz`, `GHz`
+    """
+
+    GAS = "gas"
+    """Gas.
+
+    Unit of measurement:
+    - SI / metric: `m³`
+    - USCS / imperial: `ft³`, `CCF`
+    """
+
+    HUMIDITY = "humidity"
+    """Relative humidity.
+
+    Unit of measurement: `%`
+    """
+
+    ILLUMINANCE = "illuminance"
+    """Illuminance.
+
+    Unit of measurement: `lx`
+    """
+
+    IRRADIANCE = "irradiance"
+    """Irradiance.
+
+    Unit of measurement:
+    - SI / metric: `W/m²`
+    - USCS / imperial: `BTU/(h⋅ft²)`
+    """
+
+    MOISTURE = "moisture"
+    """Moisture.
+
+    Unit of measurement: `%`
+    """
+
+    MONETARY = "monetary"
+    """Amount of money.
+
+    Unit of measurement: ISO4217 currency code
+
+    See https://en.wikipedia.org/wiki/ISO_4217#Active_codes for active codes
+    """
+
+    NITROGEN_DIOXIDE = "nitrogen_dioxide"
+    """Amount of NO2.
+
+    Unit of measurement: `µg/m³`
+    """
+
+    NITROGEN_MONOXIDE = "nitrogen_monoxide"
+    """Amount of NO.
+
+    Unit of measurement: `µg/m³`
+    """
+
+    NITROUS_OXIDE = "nitrous_oxide"
+    """Amount of N2O.
+
+    Unit of measurement: `µg/m³`
+    """
+
+    OZONE = "ozone"
+    """Amount of O3.
+
+    Unit of measurement: `µg/m³`
+    """
+
+    PM1 = "pm1"
+    """Particulate matter <= 0.1 μm.
+
+    Unit of measurement: `µg/m³`
+    """
+
+    PM10 = "pm10"
+    """Particulate matter <= 10 μm.
+
+    Unit of measurement: `µg/m³`
+    """
+
+    PM25 = "pm25"
+    """Particulate matter <= 2.5 μm.
+
+    Unit of measurement: `µg/m³`
+    """
+
+    POWER_FACTOR = "power_factor"
+    """Power factor.
+
+    Unit of measurement: `%`
+    """
+
+    POWER = "power"
+    """Power.
+
+    Unit of measurement: `W`, `kW`
+    """
+
+    PRECIPITATION = "precipitation"
+    """Precipitation.
+
+    Unit of measurement: UnitOfPrecipitationDepth
+    - SI / metric: `cm`, `mm`
+    - USCS / imperial: `in`
+    """
+
+    PRECIPITATION_INTENSITY = "precipitation_intensity"
+    """Precipitation intensity.
+
+    Unit of measurement: UnitOfVolumetricFlux
+    - SI /metric: `mm/d`, `mm/h`
+    - USCS / imperial: `in/d`, `in/h`
+    """
+
+    PRESSURE = "pressure"
+    """Pressure.
+
+    Unit of measurement:
+    - `mbar`, `cbar`, `bar`
+    - `Pa`, `hPa`, `kPa`
+    - `inHg`
+    - `psi`
+    """
+
+    REACTIVE_POWER = "reactive_power"
+    """Reactive power.
+
+    Unit of measurement: `var`
+    """
+
+    SIGNAL_STRENGTH = "signal_strength"
+    """Signal strength.
+
+    Unit of measurement: `dB`, `dBm`
+    """
+
+    SOUND_PRESSURE = "sound_pressure"
+    """Sound pressure.
+
+    Unit of measurement: `dB`, `dBA`
+    """
+
+    SPEED = "speed"
+    """Generic speed.
+
+    Unit of measurement: `SPEED_*` units or `UnitOfVolumetricFlux`
+    - SI /metric: `mm/d`, `mm/h`, `m/s`, `km/h`
+    - USCS / imperial: `in/d`, `in/h`, `ft/s`, `mph`
+    - Nautical: `kn`
+    """
+
+    SULPHUR_DIOXIDE = "sulphur_dioxide"
+    """Amount of SO2.
+
+    Unit of measurement: `µg/m³`
+    """
+
+    TEMPERATURE = "temperature"
+    """Temperature.
+
+    Unit of measurement: `°C`, `°F`
+    """
+
+    VOLATILE_ORGANIC_COMPOUNDS = "volatile_organic_compounds"
+    """Amount of VOC.
+
+    Unit of measurement: `µg/m³`
+    """
+
+    VOLTAGE = "voltage"
+    """Voltage.
+
+    Unit of measurement: `V`, `mV`
+    """
+
+    VOLUME = "volume"
+    """Generic volume.
+
+    Unit of measurement: `VOLUME_*` units
+    - SI / metric: `mL`, `L`, `m³`
+    - USCS / imperial: `ft³`, `CCF`, `fl. oz.`, `gal` (warning: volumes expressed in
+    USCS/imperial units are currently assumed to be US volumes)
+    """
+
+    WATER = "water"
+    """Water.
+
+    Unit of measurement:
+    - SI / metric: `m³`, `L`
+    - USCS / imperial: `ft³`, `CCF`, `gal` (warning: volumes expressed in
+    USCS/imperial units are currently assumed to be US volumes)
+    """
+
+    WEIGHT = "weight"
+    """Generic weight, represents a measurement of an object's mass.
+
+    Weight is used instead of mass to fit with every day language.
+
+    Unit of measurement: `MASS_*` units
+    - SI / metric: `µg`, `mg`, `g`, `kg`
+    - USCS / imperial: `oz`, `lb`
+    """
+
+    WIND_SPEED = "wind_speed"
+    """Wind speed.
+
+    Unit of measurement: `SPEED_*` units
+    - SI /metric: `m/s`, `km/h`
+    - USCS / imperial: `ft/s`, `mph`
+    - Nautical: `kn`
+    """
+
+
+DEVICE_CLASSES_SCHEMA: Final = vol.All(vol.Lower, vol.Coerce(SensorDeviceClass))
+
+# DEVICE_CLASSES is deprecated as of 2021.12
+# use the SensorDeviceClass enum instead.
+DEVICE_CLASSES: Final[list[str]] = [cls.value for cls in SensorDeviceClass]
+
+
+class SensorStateClass(StrEnum):
+    """State class for sensors."""
+
+    MEASUREMENT = "measurement"
+    """The state represents a measurement in present time."""
+
+    TOTAL = "total"
+    """The state represents a total amount.
+
+    For example: net energy consumption"""
+
+    TOTAL_INCREASING = "total_increasing"
+    """The state represents a monotonically increasing total.
+
+    For example: an amount of consumed gas"""
+
+
+STATE_CLASSES_SCHEMA: Final = vol.All(vol.Lower, vol.Coerce(SensorStateClass))
+
+
+# STATE_CLASS* is deprecated as of 2021.12
+# use the SensorStateClass enum instead.
+STATE_CLASS_MEASUREMENT: Final = "measurement"
+STATE_CLASS_TOTAL: Final = "total"
+STATE_CLASS_TOTAL_INCREASING: Final = "total_increasing"
+STATE_CLASSES: Final[list[str]] = [cls.value for cls in SensorStateClass]
+
+# Note: this needs to be aligned with frontend: OVERRIDE_SENSOR_UNITS in
+# `entity-registry-settings.ts`
+UNIT_CONVERTERS: dict[SensorDeviceClass | str | None, type[BaseUnitConverter]] = {
+    SensorDeviceClass.DATA_RATE: DataRateConverter,
+    SensorDeviceClass.DATA_SIZE: InformationConverter,
+    SensorDeviceClass.DISTANCE: DistanceConverter,
+    SensorDeviceClass.CURRENT: ElectricCurrentConverter,
+    SensorDeviceClass.GAS: VolumeConverter,
+    SensorDeviceClass.PRECIPITATION: DistanceConverter,
+    SensorDeviceClass.PRESSURE: PressureConverter,
+    SensorDeviceClass.SPEED: SpeedConverter,
+    SensorDeviceClass.TEMPERATURE: TemperatureConverter,
+    SensorDeviceClass.VOLTAGE: ElectricPotentialConverter,
+    SensorDeviceClass.VOLUME: VolumeConverter,
+    SensorDeviceClass.WATER: VolumeConverter,
+    SensorDeviceClass.WEIGHT: MassConverter,
+    SensorDeviceClass.WIND_SPEED: SpeedConverter,
+}
+
+DEVICE_CLASS_UNITS: dict[SensorDeviceClass, set[type[StrEnum] | str | None]] = {
+    SensorDeviceClass.APPARENT_POWER: set(UnitOfApparentPower),
+    SensorDeviceClass.AQI: {None},
+    SensorDeviceClass.ATMOSPHERIC_PRESSURE: set(UnitOfPressure),
+    SensorDeviceClass.BATTERY: {PERCENTAGE},
+    SensorDeviceClass.CO: {CONCENTRATION_PARTS_PER_MILLION},
+    SensorDeviceClass.CO2: {CONCENTRATION_PARTS_PER_MILLION},
+    SensorDeviceClass.CURRENT: set(UnitOfElectricCurrent),
+    SensorDeviceClass.DATA_RATE: set(UnitOfDataRate),
+    SensorDeviceClass.DATA_SIZE: set(UnitOfInformation),
+    SensorDeviceClass.DISTANCE: set(UnitOfLength),
+    SensorDeviceClass.DURATION: {
+        UnitOfTime.DAYS,
+        UnitOfTime.HOURS,
+        UnitOfTime.MINUTES,
+        UnitOfTime.SECONDS,
+    },
+    SensorDeviceClass.ENERGY: set(UnitOfEnergy),
+    SensorDeviceClass.FREQUENCY: set(UnitOfFrequency),
+    SensorDeviceClass.GAS: {
+        UnitOfVolume.CENTUM_CUBIC_FEET,
+        UnitOfVolume.CUBIC_FEET,
+        UnitOfVolume.CUBIC_METERS,
+    },
+    SensorDeviceClass.HUMIDITY: {PERCENTAGE},
+    SensorDeviceClass.ILLUMINANCE: {LIGHT_LUX},
+    SensorDeviceClass.IRRADIANCE: set(UnitOfIrradiance),
+    SensorDeviceClass.MOISTURE: {PERCENTAGE},
+    SensorDeviceClass.NITROGEN_DIOXIDE: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
+    SensorDeviceClass.NITROGEN_MONOXIDE: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
+    SensorDeviceClass.NITROUS_OXIDE: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
+    SensorDeviceClass.OZONE: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
+    SensorDeviceClass.PM1: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
+    SensorDeviceClass.PM10: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
+    SensorDeviceClass.PM25: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
+    SensorDeviceClass.POWER_FACTOR: {PERCENTAGE},
+    SensorDeviceClass.POWER: {UnitOfPower.WATT, UnitOfPower.KILO_WATT},
+    SensorDeviceClass.PRECIPITATION: set(UnitOfPrecipitationDepth),
+    SensorDeviceClass.PRECIPITATION_INTENSITY: set(UnitOfVolumetricFlux),
+    SensorDeviceClass.PRESSURE: set(UnitOfPressure),
+    SensorDeviceClass.REACTIVE_POWER: {POWER_VOLT_AMPERE_REACTIVE},
+    SensorDeviceClass.SIGNAL_STRENGTH: {
+        SIGNAL_STRENGTH_DECIBELS,
+        SIGNAL_STRENGTH_DECIBELS_MILLIWATT,
+    },
+    SensorDeviceClass.SOUND_PRESSURE: set(UnitOfSoundPressure),
+    SensorDeviceClass.SPEED: set(UnitOfSpeed).union(set(UnitOfVolumetricFlux)),
+    SensorDeviceClass.SULPHUR_DIOXIDE: {CONCENTRATION_MICROGRAMS_PER_CUBIC_METER},
+    SensorDeviceClass.TEMPERATURE: {
+        UnitOfTemperature.CELSIUS,
+        UnitOfTemperature.FAHRENHEIT,
+    },
+    SensorDeviceClass.VOLATILE_ORGANIC_COMPOUNDS: {
+        CONCENTRATION_MICROGRAMS_PER_CUBIC_METER
+    },
+    SensorDeviceClass.VOLTAGE: set(UnitOfElectricPotential),
+    SensorDeviceClass.VOLUME: set(UnitOfVolume),
+    SensorDeviceClass.WATER: {
+        UnitOfVolume.CENTUM_CUBIC_FEET,
+        UnitOfVolume.CUBIC_FEET,
+        UnitOfVolume.CUBIC_METERS,
+        UnitOfVolume.GALLONS,
+        UnitOfVolume.LITERS,
+    },
+    SensorDeviceClass.WEIGHT: set(UnitOfMass),
+    SensorDeviceClass.WIND_SPEED: set(UnitOfSpeed),
+}