Solenoidal inductors are often used in high voltage, pulsed power, and power conditioning. The following diagram shows a simple single layer solenoid of length l and radius r.

The inductance of a solenoid can be found from the following formulas:

where N is the number of turns, R is the radius of the solenoid (in inches), and l is the length of the solenoid (in inches).

where N is the number of turns, R is the radius of the solenoid (in cm), and l is the length of the solenoid (in cm).