Inductor Color Code Calculator

The Inductor Color Code Calculator decodes the color band markings found on small axial inductors — coils wound on a ferrite or ceramic core — to reveal their inductance value in microhenries (μH) and the associated tolerance range. Just as resistors use a color-band system to encode resistance, inductors use an analogous scheme to encode inductance, following standards similar to IEC 60062.

Inductors are passive components that store energy in a magnetic field when current flows through them. They are fundamental building blocks in filters, oscillators, power converters, RF circuits, and impedance matching networks. In switching power supplies (buck, boost, flyback topologies), the inductor value directly determines ripple current and output voltage regulation. In LC filters, inductance and capacitance together set the cutoff frequency. Correct identification of inductor values is therefore critical to circuit performance.

The color code for inductors follows the same digit-multiplier scheme used for resistors, but the result is expressed in microhenries (μH) rather than ohms. The first two bands represent significant digits, the third band represents the multiplier as a power of ten, and the fourth band (if present) indicates tolerance. Common tolerance values for inductors are ±5%, ±10%, and ±20%, with tighter grades used in RF and precision filter applications.

Reading inductor color bands can be more challenging than resistor bands because inductors may be physically smaller, the coil winding obscures the body, and some manufacturers use non-standard color sequences. This calculator standardizes the process: input the numeric value of each band (using the standard digit-to-color mapping: Black=0 through White=9), select the tolerance band, and instantly receive the decoded inductance value along with the min/max range.

Inductance values in common discrete inductors range from about 1 μH to several hundred mH. RF chokes used in radio frequency circuits are typically in the nH to μH range. Power inductors used in switch-mode power supplies are typically in the μH to low mH range. Audio frequency chokes and line filters can range up to hundreds of mH. Knowing which range your inductor falls in helps verify the decoded value makes physical sense.

Beyond identification, tolerance is especially important in resonant circuits. In an LC oscillator or bandpass filter, the resonant frequency is f = 1 / (2π√(LC)). A ±10% tolerance on both the inductor and capacitor can shift the resonant frequency significantly — potentially by 15–20% in worst-case combinations. For RF designs, tight-tolerance inductors (±2% or ±5%) are preferred, while power supply applications can often tolerate ±20%.

This calculator also converts the result from microhenries to millihenries for convenience, as some datasheets and design tools prefer millihenry notation. With both values displayed simultaneously, you can cross-reference directly against component databooks or sourcing databases without manual unit conversion.