diff --git a/IMU.cpp b/IMU.cpp
index 9516cee..1017059 100644
--- a/IMU.cpp
+++ b/IMU.cpp
@@ -430,9 +430,11 @@ void imuDataGet(EulerAngles *pstAngles,
   pstAngles->pitch = asinf(clampUnit(-2.0f * q1 * q3 + 2.0f * q0 * q2)) * 57.2957795f;
   pstAngles->roll = atan2f(2.0f * q2 * q3 + 2.0f * q0 * q1,
                            -2.0f * q1 * q1 - 2.0f * q2 * q2 + 1.0f) * 57.2957795f;
+  // Standard ZYX Euler: yaw = atan2(2*(q0*q3 + q1*q2), 1 - 2*(q2^2 + q3^2))
+  // Previous formula had both signs inverted → always started at 180° instead of 0°.
   const float quaternionYawDeg = wrapDegrees360(
-      atan2f(-2.0f * q1 * q2 - 2.0f * q0 * q3,
-             2.0f * q2 * q2 + 2.0f * q3 * q3 - 1.0f) * kRadToDeg);
+      atan2f(2.0f * q1 * q2 + 2.0f * q0 * q3,
+             1.0f - 2.0f * q2 * q2 - 2.0f * q3 * q3) * kRadToDeg);
 
   float headingDeg = 0.0f;
   if (useMagneticHeading &&