Dielectric Loss (dB/in):

$$ \alpha_d \approx 2.3 \times f_{GHz} \times \sqrt{E_r} \times D_f $$

Conductor Loss (dB/in) for 1/2 oz copper:

$$ \alpha_c \approx \frac{0.1 \times \sqrt{f_{GHz}}}{W_{mils}} $$

Total Loss = $(\alpha_d + \alpha_c) \times L$. Note: These are simplified first-order heuristics commonly used in high-speed digital design for FR4-like materials.