Air Core Inductor
Single-layer coil design calculator
RF / Electronics
Calculate Turns (N)
L
Inductance
l
Length
cm
r
Radius
cm
Turns (N)
Wire Dia (D)
cm
Calculate Inductance (L)
l
Length
cm
r
Radius
cm
N
Number of turns
Inductance (L)
µH
Wire Dia (D)
mm
Reference
Wheeler's Formula
L = (0.394 · r² · N²) / (9r + 10l)
- L — Inductance (µH)
- r — Radius (cm)
- l — Length (cm)
- N — Number of turns
- D — Wire diameter = l / N
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Formula valid when r > 0.67l
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Example: For a 22µH inductor with l = 2cm and r = 1cm → N ≈ 40 turns. Use wire diameter D = l/N to select the appropriate AWG wire gauge.
In this example above the diameter(D) of the wire is 0.5mm. From the AWG table the closest AWG wire size is AWG 24 which has diameter of 0.51mm. To reduce the capacitance that may develop between the wires some spacing is desirable. So selecting the next AWG will more diameter is 23 which should be selected.
Related Topics
A rough guidance of making coil to operate the inductor in the frequency range 50MHz to 150MHz, with number of turns and radius is shown below.
