diff --git a/packages/SystemUI/src/com/android/systemui/biometrics/udfps/EllipseOverlapDetector.kt b/packages/SystemUI/src/com/android/systemui/biometrics/udfps/EllipseOverlapDetector.kt
index 9847c10abd5cb..baf8d743938d7 100644
--- a/packages/SystemUI/src/com/android/systemui/biometrics/udfps/EllipseOverlapDetector.kt
+++ b/packages/SystemUI/src/com/android/systemui/biometrics/udfps/EllipseOverlapDetector.kt
@@ -22,9 +22,7 @@ import android.util.Log
 import com.android.systemui.biometrics.EllipseOverlapDetectorParams
 import com.android.systemui.dagger.SysUISingleton
 import kotlin.math.cos
-import kotlin.math.pow
 import kotlin.math.sin
-import kotlin.math.sqrt
 
 private enum class SensorPixelPosition {
     OUTSIDE, // Pixel that falls outside of sensor circle
@@ -42,8 +40,8 @@ private val TAG = "EllipseOverlapDetector"
 @SysUISingleton
 class EllipseOverlapDetector(private val params: EllipseOverlapDetectorParams) : OverlapDetector {
     override fun isGoodOverlap(touchData: NormalizedTouchData, nativeSensorBounds: Rect): Boolean {
-        // First, check if entire ellipse is within the sensor
-        if (isEllipseWithinSensor(touchData, nativeSensorBounds)) {
+        // First, check if touch is within bounding box,
+        if (nativeSensorBounds.contains(touchData.x.toInt(), touchData.y.toInt())) {
             return true
         }
 
@@ -119,28 +117,4 @@ class EllipseOverlapDetector(private val params: EllipseOverlapDetectorParams) :
 
         return result <= 1
     }
-
-    /** Returns whether the entire ellipse is contained within the sensor area */
-    private fun isEllipseWithinSensor(
-        touchData: NormalizedTouchData,
-        nativeSensorBounds: Rect
-    ): Boolean {
-        val a2 = (touchData.minor / 2.0).pow(2.0)
-        val b2 = (touchData.major / 2.0).pow(2.0)
-
-        val sin2a = sin(touchData.orientation.toDouble()).pow(2.0)
-        val cos2a = cos(touchData.orientation.toDouble()).pow(2.0)
-
-        val cx = sqrt(a2 * cos2a + b2 * sin2a)
-        val cy = sqrt(a2 * sin2a + b2 * cos2a)
-
-        val ellipseRect =
-            Rect(
-                (-cx + touchData.x).toInt(),
-                (-cy + touchData.y).toInt(),
-                (cx + touchData.x).toInt(),
-                (cy + touchData.y).toInt()
-            )
-        return nativeSensorBounds.contains(ellipseRect)
-    }
 }
diff --git a/packages/SystemUI/tests/src/com/android/systemui/biometrics/udfps/EllipseOverlapDetectorTest.kt b/packages/SystemUI/tests/src/com/android/systemui/biometrics/udfps/EllipseOverlapDetectorTest.kt
index 4b41537208da5..fb3c1854e9966 100644
--- a/packages/SystemUI/tests/src/com/android/systemui/biometrics/udfps/EllipseOverlapDetectorTest.kt
+++ b/packages/SystemUI/tests/src/com/android/systemui/biometrics/udfps/EllipseOverlapDetectorTest.kt
@@ -61,7 +61,7 @@ class EllipseOverlapDetectorTest(val testCase: TestCase) : SysuiTestCase() {
         @JvmStatic
         fun data(): List<TestCase> =
             listOf(
-                    genTestCases(
+                    genPositiveTestCases(
                         innerXs = listOf(SENSOR.left, SENSOR.right, SENSOR.centerX()),
                         innerYs = listOf(SENSOR.top, SENSOR.bottom, SENSOR.centerY()),
                         outerXs = listOf(SENSOR.left - 1, SENSOR.right + 1),
@@ -70,9 +70,7 @@ class EllipseOverlapDetectorTest(val testCase: TestCase) : SysuiTestCase() {
                         major = 300f,
                         expected = true
                     ),
-                    genTestCases(
-                        innerXs = listOf(SENSOR.left, SENSOR.right),
-                        innerYs = listOf(SENSOR.top, SENSOR.bottom),
+                    genNegativeTestCase(
                         outerXs = listOf(SENSOR.left - 1, SENSOR.right + 1),
                         outerYs = listOf(SENSOR.top - 1, SENSOR.bottom + 1),
                         minor = 100f,
@@ -107,7 +105,7 @@ private val TOUCH_DATA =
 
 private val SENSOR = Rect(100 /* left */, 200 /* top */, 300 /* right */, 400 /* bottom */)
 
-private fun genTestCases(
+private fun genPositiveTestCases(
     innerXs: List<Int>,
     innerYs: List<Int>,
     outerXs: List<Int>,
@@ -122,3 +120,15 @@ private fun genTestCases(
         }
     }
 }
+
+private fun genNegativeTestCase(
+    outerXs: List<Int>,
+    outerYs: List<Int>,
+    minor: Float,
+    major: Float,
+    expected: Boolean
+): List<EllipseOverlapDetectorTest.TestCase> {
+    return outerXs.flatMap { x ->
+        outerYs.map { y -> EllipseOverlapDetectorTest.TestCase(x, y, minor, major, expected) }
+    }
+}