diff --git a/esphome/components/a02yyuw/sensor.py b/esphome/components/a02yyuw/sensor.py
index 5232b04546..d491a51be9 100644
--- a/esphome/components/a02yyuw/sensor.py
+++ b/esphome/components/a02yyuw/sensor.py
@@ -4,11 +4,11 @@ from esphome.const import (
     STATE_CLASS_MEASUREMENT,
     ICON_ARROW_EXPAND_VERTICAL,
     DEVICE_CLASS_DISTANCE,
+    UNIT_MILLIMETER,
 )
 
 CODEOWNERS = ["@TH-Braemer"]
 DEPENDENCIES = ["uart"]
-UNIT_MILLIMETERS = "mm"
 
 a02yyuw_ns = cg.esphome_ns.namespace("a02yyuw")
 A02yyuwComponent = a02yyuw_ns.class_(
@@ -17,7 +17,7 @@ A02yyuwComponent = a02yyuw_ns.class_(
 
 CONFIG_SCHEMA = sensor.sensor_schema(
     A02yyuwComponent,
-    unit_of_measurement=UNIT_MILLIMETERS,
+    unit_of_measurement=UNIT_MILLIMETER,
     icon=ICON_ARROW_EXPAND_VERTICAL,
     accuracy_decimals=0,
     state_class=STATE_CLASS_MEASUREMENT,
diff --git a/esphome/components/hydreon_rgxx/sensor.py b/esphome/components/hydreon_rgxx/sensor.py
index 72b74bf624..fb2099c85e 100644
--- a/esphome/components/hydreon_rgxx/sensor.py
+++ b/esphome/components/hydreon_rgxx/sensor.py
@@ -12,13 +12,13 @@ from esphome.const import (
     STATE_CLASS_MEASUREMENT,
     STATE_CLASS_TOTAL_INCREASING,
     UNIT_CELSIUS,
+    UNIT_MILLIMETER,
     ICON_THERMOMETER,
 )
 
 from . import RGModel, RG15Resolution, HydreonRGxxComponent
 
 UNIT_INTENSITY = "intensity"
-UNIT_MILLIMETERS = "mm"
 UNIT_MILLIMETERS_PER_HOUR = "mm/h"
 
 CONF_ACC = "acc"
@@ -85,19 +85,19 @@ CONFIG_SCHEMA = cv.All(
             ),
             cv.Optional(CONF_RESOLUTION): cv.enum(RG15_RESOLUTION, upper=False),
             cv.Optional(CONF_ACC): sensor.sensor_schema(
-                unit_of_measurement=UNIT_MILLIMETERS,
+                unit_of_measurement=UNIT_MILLIMETER,
                 accuracy_decimals=2,
                 device_class=DEVICE_CLASS_PRECIPITATION,
                 state_class=STATE_CLASS_MEASUREMENT,
             ),
             cv.Optional(CONF_EVENT_ACC): sensor.sensor_schema(
-                unit_of_measurement=UNIT_MILLIMETERS,
+                unit_of_measurement=UNIT_MILLIMETER,
                 accuracy_decimals=2,
                 device_class=DEVICE_CLASS_PRECIPITATION,
                 state_class=STATE_CLASS_MEASUREMENT,
             ),
             cv.Optional(CONF_TOTAL_ACC): sensor.sensor_schema(
-                unit_of_measurement=UNIT_MILLIMETERS,
+                unit_of_measurement=UNIT_MILLIMETER,
                 accuracy_decimals=2,
                 device_class=DEVICE_CLASS_PRECIPITATION,
                 state_class=STATE_CLASS_TOTAL_INCREASING,
diff --git a/esphome/components/mopeka_pro_check/sensor.py b/esphome/components/mopeka_pro_check/sensor.py
index 51a515ef0c..0ba33e94de 100644
--- a/esphome/components/mopeka_pro_check/sensor.py
+++ b/esphome/components/mopeka_pro_check/sensor.py
@@ -12,6 +12,7 @@ from esphome.const import (
     CONF_TEMPERATURE,
     DEVICE_CLASS_TEMPERATURE,
     UNIT_CELSIUS,
+    UNIT_MILLIMETER,
     STATE_CLASS_MEASUREMENT,
     CONF_BATTERY_LEVEL,
     DEVICE_CLASS_BATTERY,
@@ -25,8 +26,6 @@ ICON_PROPANE_TANK = "mdi:propane-tank"
 
 TANK_TYPE_CUSTOM = "CUSTOM"
 
-UNIT_MILLIMETER = "mm"
-
 
 def small_distance(value):
     """small_distance is stored in mm"""
diff --git a/esphome/components/mopeka_std_check/sensor.py b/esphome/components/mopeka_std_check/sensor.py
index bbba798e95..ac745cf3d5 100644
--- a/esphome/components/mopeka_std_check/sensor.py
+++ b/esphome/components/mopeka_std_check/sensor.py
@@ -12,6 +12,7 @@ from esphome.const import (
     CONF_TEMPERATURE,
     DEVICE_CLASS_TEMPERATURE,
     UNIT_CELSIUS,
+    UNIT_MILLIMETER,
     STATE_CLASS_MEASUREMENT,
     CONF_BATTERY_LEVEL,
     DEVICE_CLASS_BATTERY,
@@ -26,8 +27,6 @@ ICON_PROPANE_TANK = "mdi:propane-tank"
 
 TANK_TYPE_CUSTOM = "CUSTOM"
 
-UNIT_MILLIMETER = "mm"
-
 
 def small_distance(value):
     """small_distance is stored in mm"""
diff --git a/esphome/const.py b/esphome/const.py
index ed0a9b1f64..dcb353ab1c 100644
--- a/esphome/const.py
+++ b/esphome/const.py
@@ -1035,6 +1035,7 @@ UNIT_MICROSIEMENS_PER_CENTIMETER = "µS/cm"
 UNIT_MICROSILVERTS_PER_HOUR = "µSv/h"
 UNIT_MICROTESLA = "µT"
 UNIT_MILLIGRAMS_PER_CUBIC_METER = "mg/m³"
+UNIT_MILLIMETER = "mm"
 UNIT_MILLISECOND = "ms"
 UNIT_MILLISIEMENS_PER_CENTIMETER = "mS/cm"
 UNIT_MINUTE = "min"