Rectangular Planar Spiral Coil Inductance Estimator

Coil parameters

N Number of turns (dimensionless, N ≥ 2)

A Longer outer mid-conductor side (mm)

B Shorter outer mid-conductor side (mm)

w Winding pitch (mm, w = s + g)

s Conductor width (mm)

h Conductor height / thickness (mm)

Parameter definitions

NNumber of turns or windings (N ≥ 2)
ALonger outermost mid-conductor side length
BShorter outermost mid-conductor side length
wWinding distance or pitch (w = s + g)
gGap or spacing between windings
sConductor width
hConductor height or thickness

Result

Inductance L

Press “Estimate Inductance”

microhenry (µH)

Outer sides A × B

—

Inner mid sides a × b

—

Aspect A / B

—

Gap g = w − s

—

Fill ratio ρ

—

Cross-section h / s

—

Geometry preview

conductor track dimensions A, A_in, B, B_in s = width · g = gap · w = s + g · turns drawn for clarity

Notes

The formula lowers the overall maximum error from 28% down to 5.6% compared to the FastHenry2 estimator.

This estimation is primarily based on the formulae devised by H. A. Aebischer in Inductance Formula for Rectangular Planar Spiral Inductors with Rectangular Conductor Cross Section, with required alterations regarding the geometry of rectangular planar coils and their physical structure in PCB implementation made by S. Chatterjee, School of Physics, ITMO University, Saint Petersburg, Russian Federation.

Valid designs: aspect ratio A/B up to 4.0, cross-section h/s ≤ 1, and geometric fill ratio within the published limits. Invalid combinations that would cause overlapping turns are rejected.