🌀 Planar Inductor Calculator
Estimate the inductance of a PCB spiral inductor using Mohan's modified Wheeler formula.
Coil Shape
$$L = \dfrac{K_1\,\mu_0\,N^2\,d_\text{avg}}{1 + K_2\,\rho}$$
Mohan modified Wheeler formula. ρ = (dout − din) / (dout + din), davg = (dout + din) / 2. Shape coefficients: square K₁=2.34, K₂=2.75 · hexagonal K₁=2.33, K₂=3.82 · octagonal K₁=2.25, K₂=3.55 · circular K₁=2.46, K₂=2.04.
d_in = d_out − 2N(W + S)
Used to estimate DC resistance
1 oz/ft² ≈ 35 µm
⚠ Please enter N, d_out, and d_in (d_in must be less than d_out).
Results
Validity & Notes
The Mohan modified Wheeler formula is accurate to within ~3% for fill ratios ρ between 0.1 and 0.9. It assumes air core (no magnetic substrate). Self-resonant frequency, Q factor, and parasitics are not modelled here — use EM simulation for precision RF design. DC resistance is calculated from copper resistivity ρCu = 1.724 × 10⁻⁸ Ω·m using the estimated mean turn length.