finding corner frequency using .MEASURE in LTSpice
I modified the .MEASURE command. As -3dB doesn't make sense so I specified the absolute value of voltage V(o) i.e. $$-3 = 20\log_{10}(\frac{V_o}{V_i})\\
\therefore V_o = 0.707945 \space \space[\because V_{i}=1]\\
$$
and Final command would be .MEASURE AC f FIND frequency WHEN mag(V(o))=0.7079457843841379 which gives f=158.778 printed in View &gt; Spice Error Log
Final Circuit :