Coil Inductance Calculator

Use the Coil Inductance Calculator to calculate the inductance of air-cored single-layer solenoid, multi-layer solenoid and flat spiral coils, and learn how with the integrated live example

The formula for calculating the inductance of an air-core single-layer solenoid is:

$L=\frac{r^2N^2}{9r+10l}\; \mu H$

The formula for calculating the inductance of an air-core multi-layer solenoid is:

$L=\frac{0.8(r^2N^2)}{6r+9l+10d}\; \mu H$

The formula for calculating the inductance of an air-core flat spiral coil is:

$L=\frac{r^2N^2}{8r+11d}\; \mu H$

Where
N = Number of turns
r = Coil radius in inches
l = Coil length in inches
d = Winding depth in inches
L = Inductance in microhenrys (μH)

Coil Inductance Calculator Diagram — *Coil dimensions for calculating inductance*

Using the Coil Inductance Calculator

Coil Geometry: Select the geometry of your coil from the list. You can choose from single-layer solenoid, multi-layer solenoid and flat spiral coil forms

Length: Enter the coil length, measured as depicted in the diagram above

Diameter: Enter the coil diameter, measured as depicted in the diagram above

Depth: Enter the winding depth, as depicted in the diagram. This does not apply to a single-layer solenoid coil

Number Of Turns: Enter the total number of turns

How To Calculate Coil Inductance: This feature displays a live example of how to calculate self-inductance using the figures that you enter

The result is calculated and updated automatically as you enter different numbers or change between the input fields. If the calculated result hasn’t updated after you’ve finished entering your values, click or tap on the result.

Reference: ARRL – The Radio Amateur’s Handbook