Helical Coil Calculator

Your details

Outer-to-outer diameter of the winding measured at the coil centreline. In imperial mode, enter inches; in metric, millimetres.
mm
Diameter of the bare conductor (not including insulation).
mm
Total number of complete loops in the coil.
turns
Gap between adjacent turns, measured edge-to-edge. Set to 0 for a close-wound coil.
mm
DC or RMS current through the coil. Used to calculate magnetic field, stored energy, and time constant.
A
Distributed capacitance of the coil (self-capacitance). Used to compute the self-resonant frequency.
pF
Resistivity used to calculate DC wire resistance. Copper (1.724e-8 ohm*m) is the standard for most RF and power inductors.
Inductance (L)Low-frequency RF range
8.1455uH

Single-layer inductance via Wheeler (1928) formula

Coil height (H)30
Wire length (Lw)1,885.19
Wire volume (V)1,480.628
DC resistance (R)0.0414ohm
Magnetic field (H)666.666A/m
Flux density (B)0.8378mT
Stored energy (E)4.0728uJ
Time constant (tau)196.8414us
Resonant frequency17,634.38kHz
Coil height30.00 mm
Wire length1885.19 mm
Wire volume1480.628 mm³
Inductance (uH)8.1455
Resistance (ohm)0.0414
Energy (uJ)4.0728

Inductance: 8.1455 uH

  • Inductance of 8.1455 uH falls in the low RF (0.1-10 uH) range.
  • DC resistance is 0.0414 ohm. Lower resistance means higher Q-factor and less power loss.
  • Self-resonant frequency is 17634.38 kHz. The coil behaves as an inductor only well below this frequency.
  • The L/R time constant is 196.84 us: the current rises to ~63 % of its final value in this time.
  • Axial flux density at the coil centre is 0.8378 mT (solenoid approximation, valid when coil height is comparable to or greater than diameter).

Next stepTo double the inductance, multiply the number of turns by sqrt(2) (about 28 turns), keeping the same geometry.

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