diff --git a/homeassistant/components/ambient_station/__init__.py b/homeassistant/components/ambient_station/__init__.py
index ac8ae18a657..8658c3d04b9 100644
--- a/homeassistant/components/ambient_station/__init__.py
+++ b/homeassistant/components/ambient_station/__init__.py
@@ -19,6 +19,7 @@ from homeassistant.const import (
     EVENT_HOMEASSISTANT_STOP,
     PERCENTAGE,
     POWER_WATT,
+    PRESSURE_INHG,
     SPEED_MILES_PER_HOUR,
     TEMP_FAHRENHEIT,
 )
@@ -143,8 +144,8 @@ TYPE_WINDSPEEDMPH = "windspeedmph"
 TYPE_YEARLYRAININ = "yearlyrainin"
 SENSOR_TYPES = {
     TYPE_24HOURRAININ: ("24 Hr Rain", "in", TYPE_SENSOR, None),
-    TYPE_BAROMABSIN: ("Abs Pressure", "inHg", TYPE_SENSOR, "pressure"),
-    TYPE_BAROMRELIN: ("Rel Pressure", "inHg", TYPE_SENSOR, "pressure"),
+    TYPE_BAROMABSIN: ("Abs Pressure", PRESSURE_INHG, TYPE_SENSOR, "pressure"),
+    TYPE_BAROMRELIN: ("Rel Pressure", PRESSURE_INHG, TYPE_SENSOR, "pressure"),
     TYPE_BATT10: ("Battery 10", None, TYPE_BINARY_SENSOR, "battery"),
     TYPE_BATT1: ("Battery 1", None, TYPE_BINARY_SENSOR, "battery"),
     TYPE_BATT2: ("Battery 2", None, TYPE_BINARY_SENSOR, "battery"),
diff --git a/homeassistant/components/bloomsky/sensor.py b/homeassistant/components/bloomsky/sensor.py
index 812efe7697e..eaa03ef2f3b 100644
--- a/homeassistant/components/bloomsky/sensor.py
+++ b/homeassistant/components/bloomsky/sensor.py
@@ -8,6 +8,8 @@ from homeassistant.const import (
     AREA_SQUARE_METERS,
     CONF_MONITORED_CONDITIONS,
     PERCENTAGE,
+    PRESSURE_INHG,
+    PRESSURE_MBAR,
     TEMP_CELSIUS,
     TEMP_FAHRENHEIT,
 )
@@ -32,7 +34,7 @@ SENSOR_TYPES = [
 SENSOR_UNITS_IMPERIAL = {
     "Temperature": TEMP_FAHRENHEIT,
     "Humidity": PERCENTAGE,
-    "Pressure": "inHg",
+    "Pressure": PRESSURE_INHG,
     "Luminance": f"cd/{AREA_SQUARE_METERS}",
     "Voltage": "mV",
 }
@@ -41,7 +43,7 @@ SENSOR_UNITS_IMPERIAL = {
 SENSOR_UNITS_METRIC = {
     "Temperature": TEMP_CELSIUS,
     "Humidity": PERCENTAGE,
-    "Pressure": "mbar",
+    "Pressure": PRESSURE_MBAR,
     "Luminance": f"cd/{AREA_SQUARE_METERS}",
     "Voltage": "mV",
 }
diff --git a/homeassistant/components/bom/sensor.py b/homeassistant/components/bom/sensor.py
index 56406b29e82..848be51cc8f 100644
--- a/homeassistant/components/bom/sensor.py
+++ b/homeassistant/components/bom/sensor.py
@@ -22,6 +22,7 @@ from homeassistant.const import (
     LENGTH_KILOMETERS,
     LENGTH_METERS,
     PERCENTAGE,
+    PRESSURE_MBAR,
     SPEED_KILOMETERS_PER_HOUR,
     TEMP_CELSIUS,
 )
@@ -66,7 +67,7 @@ SENSOR_TYPES = {
     "gust_kt": ["Wind Gust kt", "kt"],
     "air_temp": ["Air Temp C", TEMP_CELSIUS],
     "dewpt": ["Dew Point C", TEMP_CELSIUS],
-    "press": ["Pressure mb", "mbar"],
+    "press": ["Pressure mb", PRESSURE_MBAR],
     "press_qnh": ["Pressure qnh", "qnh"],
     "press_msl": ["Pressure msl", "msl"],
     "press_tend": ["Pressure Tend", None],
diff --git a/homeassistant/components/buienradar/sensor.py b/homeassistant/components/buienradar/sensor.py
index ba0063ebb85..d1d1f0cf632 100644
--- a/homeassistant/components/buienradar/sensor.py
+++ b/homeassistant/components/buienradar/sensor.py
@@ -31,6 +31,7 @@ from homeassistant.const import (
     IRRADIATION_WATTS_PER_SQUARE_METER,
     LENGTH_KILOMETERS,
     PERCENTAGE,
+    PRESSURE_HPA,
     SPEED_KILOMETERS_PER_HOUR,
     TEMP_CELSIUS,
     TIME_HOURS,
@@ -78,7 +79,7 @@ SENSOR_TYPES = {
     "windforce": ["Wind force", "Bft", "mdi:weather-windy"],
     "winddirection": ["Wind direction", None, "mdi:compass-outline"],
     "windazimuth": ["Wind direction azimuth", DEGREE, "mdi:compass-outline"],
-    "pressure": ["Pressure", "hPa", "mdi:gauge"],
+    "pressure": ["Pressure", PRESSURE_HPA, "mdi:gauge"],
     "visibility": ["Visibility", LENGTH_KILOMETERS, None],
     "windgust": ["Wind gust", SPEED_KILOMETERS_PER_HOUR, "mdi:weather-windy"],
     "precipitation": ["Precipitation", f"mm/{TIME_HOURS}", "mdi:weather-pouring"],
diff --git a/homeassistant/components/darksky/sensor.py b/homeassistant/components/darksky/sensor.py
index e167f16b4e4..48ceffbac50 100644
--- a/homeassistant/components/darksky/sensor.py
+++ b/homeassistant/components/darksky/sensor.py
@@ -19,6 +19,7 @@ from homeassistant.const import (
     LENGTH_CENTIMETERS,
     LENGTH_KILOMETERS,
     PERCENTAGE,
+    PRESSURE_MBAR,
     SPEED_KILOMETERS_PER_HOUR,
     SPEED_METERS_PER_SECOND,
     SPEED_MILES_PER_HOUR,
@@ -219,11 +220,11 @@ SENSOR_TYPES = {
     ],
     "pressure": [
         "Pressure",
-        "mbar",
-        "mbar",
-        "mbar",
-        "mbar",
-        "mbar",
+        PRESSURE_MBAR,
+        PRESSURE_MBAR,
+        PRESSURE_MBAR,
+        PRESSURE_MBAR,
+        PRESSURE_MBAR,
         "mdi:gauge",
         ["currently", "hourly", "daily"],
     ],
diff --git a/homeassistant/components/envirophat/sensor.py b/homeassistant/components/envirophat/sensor.py
index 4813fd47a92..873d9935ee8 100644
--- a/homeassistant/components/envirophat/sensor.py
+++ b/homeassistant/components/envirophat/sensor.py
@@ -6,7 +6,13 @@ import logging
 import voluptuous as vol
 
 from homeassistant.components.sensor import PLATFORM_SCHEMA
-from homeassistant.const import CONF_DISPLAY_OPTIONS, CONF_NAME, TEMP_CELSIUS, VOLT
+from homeassistant.const import (
+    CONF_DISPLAY_OPTIONS,
+    CONF_NAME,
+    PRESSURE_HPA,
+    TEMP_CELSIUS,
+    VOLT,
+)
 import homeassistant.helpers.config_validation as cv
 from homeassistant.helpers.entity import Entity
 from homeassistant.util import Throttle
@@ -30,7 +36,7 @@ SENSOR_TYPES = {
     "magnetometer_y": ["magnetometer_y", " ", "mdi:magnet"],
     "magnetometer_z": ["magnetometer_z", " ", "mdi:magnet"],
     "temperature": ["temperature", TEMP_CELSIUS, "mdi:thermometer"],
-    "pressure": ["pressure", "hPa", "mdi:gauge"],
+    "pressure": ["pressure", PRESSURE_HPA, "mdi:gauge"],
     "voltage_0": ["voltage_0", VOLT, "mdi:flash"],
     "voltage_1": ["voltage_1", VOLT, "mdi:flash"],
     "voltage_2": ["voltage_2", VOLT, "mdi:flash"],
diff --git a/homeassistant/components/homematic/sensor.py b/homeassistant/components/homematic/sensor.py
index 51a88bd1207..121b3af5d81 100644
--- a/homeassistant/components/homematic/sensor.py
+++ b/homeassistant/components/homematic/sensor.py
@@ -11,6 +11,7 @@ from homeassistant.const import (
     FREQUENCY_HERTZ,
     PERCENTAGE,
     POWER_WATT,
+    PRESSURE_HPA,
     SPEED_KILOMETERS_PER_HOUR,
     TEMP_CELSIUS,
     VOLT,
@@ -59,7 +60,7 @@ HM_UNIT_HA_CAST = {
     "WIND_DIRECTION": DEGREE,
     "WIND_DIRECTION_RANGE": DEGREE,
     "SUNSHINEDURATION": "#",
-    "AIR_PRESSURE": "hPa",
+    "AIR_PRESSURE": PRESSURE_HPA,
     "FREQUENCY": FREQUENCY_HERTZ,
     "VALUE": "#",
     "VALVE_STATE": PERCENTAGE,
diff --git a/homeassistant/components/isy994/const.py b/homeassistant/components/isy994/const.py
index 375f4e4aa73..75c7b3b9de1 100644
--- a/homeassistant/components/isy994/const.py
+++ b/homeassistant/components/isy994/const.py
@@ -60,7 +60,9 @@ from homeassistant.const import (
     MASS_POUNDS,
     PERCENTAGE,
     POWER_WATT,
+    PRESSURE_HPA,
     PRESSURE_INHG,
+    PRESSURE_MBAR,
     SERVICE_LOCK,
     SERVICE_UNLOCK,
     SPEED_KILOMETERS_PER_HOUR,
@@ -411,8 +413,8 @@ UOM_FRIENDLY_NAME = {
     "113": "",  # raw 3-byte signed value
     "114": "",  # raw 4-byte signed value
     "116": LENGTH_MILES,
-    "117": "mbar",
-    "118": "hPa",
+    "117": PRESSURE_MBAR,
+    "118": PRESSURE_HPA,
     "119": f"{POWER_WATT}{TIME_HOURS}",
     "120": f"{LENGTH_INCHES}/{TIME_DAYS}",
 }
diff --git a/homeassistant/components/luftdaten/__init__.py b/homeassistant/components/luftdaten/__init__.py
index 9d184969139..91e9c96d429 100644
--- a/homeassistant/components/luftdaten/__init__.py
+++ b/homeassistant/components/luftdaten/__init__.py
@@ -13,6 +13,7 @@ from homeassistant.const import (
     CONF_SENSORS,
     CONF_SHOW_ON_MAP,
     PERCENTAGE,
+    PRESSURE_PA,
     TEMP_CELSIUS,
 )
 from homeassistant.core import callback
@@ -44,8 +45,8 @@ TOPIC_UPDATE = f"{DOMAIN}_data_update"
 SENSORS = {
     SENSOR_TEMPERATURE: ["Temperature", "mdi:thermometer", TEMP_CELSIUS],
     SENSOR_HUMIDITY: ["Humidity", "mdi:water-percent", PERCENTAGE],
-    SENSOR_PRESSURE: ["Pressure", "mdi:arrow-down-bold", "Pa"],
-    SENSOR_PRESSURE_AT_SEALEVEL: ["Pressure at sealevel", "mdi:download", "Pa"],
+    SENSOR_PRESSURE: ["Pressure", "mdi:arrow-down-bold", PRESSURE_PA],
+    SENSOR_PRESSURE_AT_SEALEVEL: ["Pressure at sealevel", "mdi:download", PRESSURE_PA],
     SENSOR_PM10: [
         "PM10",
         "mdi:thought-bubble",
diff --git a/homeassistant/components/opentherm_gw/const.py b/homeassistant/components/opentherm_gw/const.py
index a32a2199760..3ff1577c436 100644
--- a/homeassistant/components/opentherm_gw/const.py
+++ b/homeassistant/components/opentherm_gw/const.py
@@ -5,6 +5,7 @@ from homeassistant.components.binary_sensor import DEVICE_CLASS_PROBLEM
 from homeassistant.const import (
     DEVICE_CLASS_TEMPERATURE,
     PERCENTAGE,
+    PRESSURE_BAR,
     TEMP_CELSIUS,
     TIME_HOURS,
     TIME_MINUTES,
@@ -39,7 +40,6 @@ SERVICE_SET_MAX_MOD = "set_max_modulation"
 SERVICE_SET_OAT = "set_outside_temperature"
 SERVICE_SET_SB_TEMP = "set_setback_temperature"
 
-UNIT_BAR = "bar"
 UNIT_KW = "kW"
 UNIT_L_MIN = f"L/{TIME_MINUTES}"
 
@@ -152,7 +152,11 @@ SENSOR_INFO = {
         "Room Setpoint {}",
     ],
     gw_vars.DATA_REL_MOD_LEVEL: [None, PERCENTAGE, "Relative Modulation Level {}"],
-    gw_vars.DATA_CH_WATER_PRESS: [None, UNIT_BAR, "Central Heating Water Pressure {}"],
+    gw_vars.DATA_CH_WATER_PRESS: [
+        None,
+        PRESSURE_BAR,
+        "Central Heating Water Pressure {}",
+    ],
     gw_vars.DATA_DHW_FLOW_RATE: [None, UNIT_L_MIN, "Hot Water Flow Rate {}"],
     gw_vars.DATA_ROOM_SETPOINT_2: [
         DEVICE_CLASS_TEMPERATURE,
diff --git a/homeassistant/components/point/sensor.py b/homeassistant/components/point/sensor.py
index 4ac8f0c1832..9436877e434 100644
--- a/homeassistant/components/point/sensor.py
+++ b/homeassistant/components/point/sensor.py
@@ -7,6 +7,7 @@ from homeassistant.const import (
     DEVICE_CLASS_PRESSURE,
     DEVICE_CLASS_TEMPERATURE,
     PERCENTAGE,
+    PRESSURE_HPA,
     TEMP_CELSIUS,
 )
 from homeassistant.helpers.dispatcher import async_dispatcher_connect
@@ -21,7 +22,7 @@ DEVICE_CLASS_SOUND = "sound_level"
 
 SENSOR_TYPES = {
     DEVICE_CLASS_TEMPERATURE: (None, 1, TEMP_CELSIUS),
-    DEVICE_CLASS_PRESSURE: (None, 0, "hPa"),
+    DEVICE_CLASS_PRESSURE: (None, 0, PRESSURE_HPA),
     DEVICE_CLASS_HUMIDITY: (None, 1, PERCENTAGE),
     DEVICE_CLASS_SOUND: ("mdi:ear-hearing", 1, "dBa"),
 }
diff --git a/homeassistant/components/wunderground/sensor.py b/homeassistant/components/wunderground/sensor.py
index 2d9c4f5c9c1..6699c2f7e1d 100644
--- a/homeassistant/components/wunderground/sensor.py
+++ b/homeassistant/components/wunderground/sensor.py
@@ -24,6 +24,7 @@ from homeassistant.const import (
     LENGTH_KILOMETERS,
     LENGTH_MILES,
     PERCENTAGE,
+    PRESSURE_INHG,
     SPEED_KILOMETERS_PER_HOUR,
     SPEED_MILES_PER_HOUR,
     TEMP_CELSIUS,
@@ -406,7 +407,7 @@ SENSOR_TYPES = {
         "Precipitation Today", "precip_today_string", "mdi:umbrella"
     ),
     "pressure_in": WUCurrentConditionsSensorConfig(
-        "Pressure", "pressure_in", "mdi:gauge", "inHg", device_class="pressure"
+        "Pressure", "pressure_in", "mdi:gauge", PRESSURE_INHG, device_class="pressure"
     ),
     "pressure_mb": WUCurrentConditionsSensorConfig(
         "Pressure", "pressure_mb", "mdi:gauge", "mb", device_class="pressure"
diff --git a/homeassistant/components/xiaomi_aqara/sensor.py b/homeassistant/components/xiaomi_aqara/sensor.py
index 576e99eab4b..ed1792a5fdb 100644
--- a/homeassistant/components/xiaomi_aqara/sensor.py
+++ b/homeassistant/components/xiaomi_aqara/sensor.py
@@ -11,6 +11,7 @@ from homeassistant.const import (
     DEVICE_CLASS_TEMPERATURE,
     PERCENTAGE,
     POWER_WATT,
+    PRESSURE_HPA,
     TEMP_CELSIUS,
 )
 
@@ -24,7 +25,7 @@ SENSOR_TYPES = {
     "humidity": [PERCENTAGE, None, DEVICE_CLASS_HUMIDITY],
     "illumination": ["lm", None, DEVICE_CLASS_ILLUMINANCE],
     "lux": ["lx", None, DEVICE_CLASS_ILLUMINANCE],
-    "pressure": ["hPa", None, DEVICE_CLASS_PRESSURE],
+    "pressure": [PRESSURE_HPA, None, DEVICE_CLASS_PRESSURE],
     "bed_activity": ["μm", None, None],
     "load_power": [POWER_WATT, None, DEVICE_CLASS_POWER],
 }
diff --git a/homeassistant/components/zamg/sensor.py b/homeassistant/components/zamg/sensor.py
index 9372be58493..4852e874672 100644
--- a/homeassistant/components/zamg/sensor.py
+++ b/homeassistant/components/zamg/sensor.py
@@ -21,6 +21,7 @@ from homeassistant.const import (
     DEGREE,
     LENGTH_METERS,
     PERCENTAGE,
+    PRESSURE_HPA,
     SPEED_KILOMETERS_PER_HOUR,
     TEMP_CELSIUS,
     __version__,
@@ -42,8 +43,8 @@ DEFAULT_NAME = "zamg"
 MIN_TIME_BETWEEN_UPDATES = timedelta(minutes=10)
 
 SENSOR_TYPES = {
-    "pressure": ("Pressure", "hPa", "LDstat hPa", float),
-    "pressure_sealevel": ("Pressure at Sea Level", "hPa", "LDred hPa", float),
+    "pressure": ("Pressure", PRESSURE_HPA, "LDstat hPa", float),
+    "pressure_sealevel": ("Pressure at Sea Level", PRESSURE_HPA, "LDred hPa", float),
     "humidity": ("Humidity", PERCENTAGE, "RF %", int),
     "wind_speed": (
         "Wind Speed",
diff --git a/homeassistant/components/zha/sensor.py b/homeassistant/components/zha/sensor.py
index 6e2878f371b..215299ca34f 100644
--- a/homeassistant/components/zha/sensor.py
+++ b/homeassistant/components/zha/sensor.py
@@ -16,6 +16,7 @@ from homeassistant.const import (
     ATTR_UNIT_OF_MEASUREMENT,
     PERCENTAGE,
     POWER_WATT,
+    PRESSURE_HPA,
     STATE_UNKNOWN,
     TEMP_CELSIUS,
 )
@@ -266,7 +267,7 @@ class Pressure(Sensor):
     SENSOR_ATTR = "measured_value"
     _device_class = DEVICE_CLASS_PRESSURE
     _decimals = 0
-    _unit = "hPa"
+    _unit = PRESSURE_HPA
 
 
 @STRICT_MATCH(channel_names=CHANNEL_TEMPERATURE)
diff --git a/tests/components/zha/test_sensor.py b/tests/components/zha/test_sensor.py
index 7cba51b3e5c..1c7d85c4528 100644
--- a/tests/components/zha/test_sensor.py
+++ b/tests/components/zha/test_sensor.py
@@ -16,6 +16,7 @@ from homeassistant.const import (
     CONF_UNIT_SYSTEM_METRIC,
     PERCENTAGE,
     POWER_WATT,
+    PRESSURE_HPA,
     STATE_UNAVAILABLE,
     STATE_UNKNOWN,
     TEMP_CELSIUS,
@@ -48,10 +49,10 @@ async def async_test_temperature(hass, cluster, entity_id):
 async def async_test_pressure(hass, cluster, entity_id):
     """Test pressure sensor."""
     await send_attributes_report(hass, cluster, {1: 1, 0: 1000, 2: 10000})
-    assert_state(hass, entity_id, "1000", "hPa")
+    assert_state(hass, entity_id, "1000", PRESSURE_HPA)
 
     await send_attributes_report(hass, cluster, {0: 1000, 20: -1, 16: 10000})
-    assert_state(hass, entity_id, "1000", "hPa")
+    assert_state(hass, entity_id, "1000", PRESSURE_HPA)
 
 
 async def async_test_illuminance(hass, cluster, entity_id):
diff --git a/tests/testing_config/custom_components/test/sensor.py b/tests/testing_config/custom_components/test/sensor.py
index 8d0cdf6ac93..7cb8bb070b1 100644
--- a/tests/testing_config/custom_components/test/sensor.py
+++ b/tests/testing_config/custom_components/test/sensor.py
@@ -4,7 +4,7 @@ Provide a mock sensor platform.
 Call init before using it in your tests to ensure clean test data.
 """
 import homeassistant.components.sensor as sensor
-from homeassistant.const import PERCENTAGE
+from homeassistant.const import PERCENTAGE, PRESSURE_HPA
 
 from tests.common import MockEntity
 
@@ -18,7 +18,7 @@ UNITS_OF_MEASUREMENT = {
     sensor.DEVICE_CLASS_SIGNAL_STRENGTH: "dB",  # signal strength (dB/dBm)
     sensor.DEVICE_CLASS_TEMPERATURE: "C",  # temperature (C/F)
     sensor.DEVICE_CLASS_TIMESTAMP: "hh:mm:ss",  # timestamp (ISO8601)
-    sensor.DEVICE_CLASS_PRESSURE: "hPa",  # pressure (hPa/mbar)
+    sensor.DEVICE_CLASS_PRESSURE: PRESSURE_HPA,  # pressure (hPa/mbar)
     sensor.DEVICE_CLASS_POWER: "kW",  # power (W/kW)
     sensor.DEVICE_CLASS_CURRENT: "A",  # current (A)
     sensor.DEVICE_CLASS_ENERGY: "kWh",  # energy (Wh/kWh)