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
The formula for calculating the inductance of an air-core single-layer solenoid is:
The formula for calculating the inductance of an air-core multi-layer solenoid is:
The formula for calculating the inductance of an air-core flat spiral coil is:
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)

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
Selecting units: You can choose your preferred units of measurement through selecting the units cells and clicking the downwards pointing arrow to display a list of available options
Learn As You Go: This feature displays a live example of how to calculate self-inductance using the figures that you enter
Reference: ARRL – The Radio Amateur’s Handbook