Helical Coil Calculator

Helical Coil Calculator

Calculate the inductance of a single-layer helical coil using Wheeler's formula.

Last updated: March 2026 | By ForgeCalc Engineering

Calculated Inductance
1.724
μH (Microhenries)

What is a Helical Coil?

A helical coil, or solenoid, is a wire wound into a helical shape. When an electric current passes through it, it creates a magnetic field. Inductance is the property of the coil that opposes changes in current.

Single-layer helical coils are fundamental components in radio frequency (RF) circuits, power supplies, and various electronic sensors. Their inductance depends on the physical dimensions and the number of turns.

How to Calculate Inductance

Wheeler's Inductance Formula

L = (n² * r²) / (9r + 10l)
  • L = Inductance in microhenries (μH)
  • n = Number of turns
  • r = Mean radius of the coil in inches
  • l = Length of the coil in inches

Frequently Asked Questions

How accurate is Wheeler's formula?

Wheeler's formula is accurate to within 1% for coils where the length is greater than 0.8 times the radius (l > 0.8r).

Does wire thickness matter?

For simple inductance calculations, wire thickness is often ignored, but it affects the 'Q factor' and parasitic capacitance of the coil.

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