diff --git a/packages/SystemUI/compose/core/Android.bp b/packages/SystemUI/compose/core/Android.bp
index 510fa1e..42d088f 100644
--- a/packages/SystemUI/compose/core/Android.bp
+++ b/packages/SystemUI/compose/core/Android.bp
@@ -34,7 +34,9 @@
 
         "androidx.compose.runtime_runtime",
         "androidx.compose.material3_material3",
+        "androidx.compose.material3_material3-window-size-class",
         "androidx.savedstate_savedstate",
+        "androidx.window_window",
     ],
 
     kotlincflags: ["-Xjvm-default=all"],
diff --git a/packages/SystemUI/compose/core/src/com/android/compose/theme/PlatformTheme.kt b/packages/SystemUI/compose/core/src/com/android/compose/theme/PlatformTheme.kt
index b4e90d6..0661870 100644
--- a/packages/SystemUI/compose/core/src/com/android/compose/theme/PlatformTheme.kt
+++ b/packages/SystemUI/compose/core/src/com/android/compose/theme/PlatformTheme.kt
@@ -29,6 +29,8 @@
 import com.android.compose.theme.typography.TypefaceTokens
 import com.android.compose.theme.typography.TypographyTokens
 import com.android.compose.theme.typography.platformTypography
+import com.android.compose.windowsizeclass.LocalWindowSizeClass
+import com.android.compose.windowsizeclass.calculateWindowSizeClass
 
 /** The Material 3 theme that should wrap all Platform Composables. */
 @Composable
@@ -51,10 +53,12 @@
         remember(typefaceNames) {
             platformTypography(TypographyTokens(TypeScaleTokens(TypefaceTokens(typefaceNames))))
         }
+    val windowSizeClass = calculateWindowSizeClass()
 
     MaterialTheme(colorScheme, typography = typography) {
         CompositionLocalProvider(
             LocalAndroidColorScheme provides androidColorScheme,
+            LocalWindowSizeClass provides windowSizeClass,
         ) {
             content()
         }
diff --git a/packages/SystemUI/compose/core/src/com/android/compose/windowsizeclass/WindowSizeClass.kt b/packages/SystemUI/compose/core/src/com/android/compose/windowsizeclass/WindowSizeClass.kt
new file mode 100644
index 0000000..4674d6e
--- /dev/null
+++ b/packages/SystemUI/compose/core/src/com/android/compose/windowsizeclass/WindowSizeClass.kt
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.compose.windowsizeclass
+
+import androidx.compose.material3.windowsizeclass.ExperimentalMaterial3WindowSizeClassApi
+import androidx.compose.material3.windowsizeclass.WindowSizeClass
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.staticCompositionLocalOf
+import androidx.compose.ui.graphics.toComposeRect
+import androidx.compose.ui.platform.LocalConfiguration
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.platform.LocalDensity
+import androidx.window.layout.WindowMetricsCalculator
+
+val LocalWindowSizeClass =
+    staticCompositionLocalOf<WindowSizeClass> {
+        throw IllegalStateException(
+            "No WindowSizeClass configured. Make sure to use LocalWindowSizeClass in a Composable" +
+                " surrounded by a PlatformTheme {}."
+        )
+    }
+
+@OptIn(ExperimentalMaterial3WindowSizeClassApi::class)
+@Composable
+fun calculateWindowSizeClass(): WindowSizeClass {
+    // Observe view configuration changes and recalculate the size class on each change.
+    LocalConfiguration.current
+    val density = LocalDensity.current
+    val context = LocalContext.current
+    val metrics = WindowMetricsCalculator.getOrCreate().computeCurrentWindowMetrics(context)
+    val size = with(density) { metrics.bounds.toComposeRect().size.toDpSize() }
+    return WindowSizeClass.calculateFromSize(size)
+}