- Published 12 Jun 2025
- Last Modified 20 Aug 2025
- 3 min
Inductance Unit Conversion Calculator
Whether you're working on a custom inductor, adjusting a high-frequency circuit, or designing a transformer or inductance motor, it's important to know the exact inductance value. Our free inductance calculator makes it quick and easy. All you have to do is choose your input value and units and we’ll give you the output units within seconds!
What is Inductance?
Inductance is a property of an electrical circuit that describes how it resists changes in electric current, especially in components like coils and inductors. When current flows through a coil of wire, it creates a magnetic field around it. If the current changes, the magnetic field also changes, which in turn creates a voltage that opposes that change.
Why is it Important to Calculate Inductance?
Calculating inductance is essential for proper circuit function, because if the value is too high or low it can cause voltage spikes, overheating and signal distortion, leading to safety concerns and damage. Calculating inductance also informs your decision on what performance limits and which materials and dimensions to use when building and designing inductors, transformers or coils for electric motors.
Inductance Formula
Wondering what the formula for inductance is? Inductance depends on the number of turns and the geometry of the coil, and as there are multiple types of coil, that means there is more than one formula to calculate inductance. The two most common formulas are the solenoid and toroidal. Check out how they are calculated below:
Solenoid Formula
The solenoid formula is used for long, cylindrical coils where the coil length is much greater than its diameter, the coil has a uniform shape, and the magnetic field lines remain mostly inside the coil.
Formula: L = µ₀ × N² × A/l
L = Inductance
μ0 = Permeability of free space
N = Number of turns of the coil
A = Cross-sectional area of the coil
l = length of the coil
Toroidal Formula
This formula is used for toroidal coils, which are shaped like a doughnut. Toroidal coils are compact and boast a reduced electromagnetic interference, making them perfect for power electronics. In toroidal coils, the wire is wound around a circular ring and the magnetic fields are entirely inside the core.
Formula: L = (μ × N² × A) / (2π × r)
L = Inductance
μ0 = Permeability of free space
N = Number of turns of the coil
A = Cross-sectional area of the coil
(r) = mean radius of the centre of the ring (toroid)
