Calculated using the Modified Wheeler Formula for planar spiral inductors (Mohan et al., 1999).

$L = K_1 \cdot \mu_0 \cdot \frac{N^2 \cdot d_{avg}}{1 + K_2 \cdot \rho}$

• $d_{avg} = (d_{out} + d_{in}) / 2$
• Fill Ratio $\rho = (d_{out} - d_{in}) / (d_{out} + d_{in})$
• Square: $K_1 = 2.34, K_2 = 2.75$
• Hexagonal: $K_1 = 2.33, K_2 = 3.82$
• Octagonal: $K_1 = 2.25, K_2 = 3.55$