Inductor Color Code Calculator
Read the color bands on axial inductors (chokes) and get the inductance in µH, mH and nH with the tolerance range — or find the bands for a given inductance value.
How it works
L = (digit 1 digit 2) × 10^(multiplier) µH · digits: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9 · multiplier gold ×0.1, silver ×0.01 · tolerance: black ±20%, brown ±1%, red ±2%, orange ±3%, yellow ±4%, gold ±5%, silver ±10%, no band ±20%
Axial (resistor-shaped) inductors and RF chokes use the same digit colors as resistors, but the result is in microhenries rather than ohms, and the tolerance band uses its own table (black or no band ±20%, silver ±10%, gold ±5%). Some military-style chokes add a wide silver band at the start to identify them as inductors — skip it and read the next four. Values below 10 µH use a gold multiplier or a gold band as the decimal point.
Worked example
An axial choke banded yellow, violet, black, silver: 4 and 7 = 47, × 1 µH = 47 µH, silver = ±10%, so 42.3–51.7 µH. That is 0.047 mH or 47,000 nH — a typical value for a switching-regulator or audio filter choke.
Sources: Electronic color code — Wikipedia · MIL-PRF-15305 Coils, fixed and variable, radio frequency
Frequently asked questions
Is the inductor color code the same as the resistor code?
The digit colors are identical, but the unit is µH instead of Ω and the tolerance colors differ (black means ±20% on an inductor). Multipliers rarely go above orange (×1,000 µH) because large inductances do not come in small axial bodies.
How do I tell an inductor from a resistor?
Inductors usually have a fatter, often green or light-blue, glossy body, and many have a wide silver first band (MIL-spec identifier). A multimeter on the ohms range reads almost zero across an inductor but the coded value across a resistor.
What if there is a gold band in the middle?
On low values a gold band between the digits acts as a decimal point: red, gold, red = 2.2 µH. In the third position gold means ×0.1 (e.g. brown, black, gold = 1.0 µH).
Does the color code give the current rating?
No — only inductance and tolerance. The saturation current and DC resistance depend on the series and size, so look up the part in the manufacturer’s datasheet before using it in a power circuit.
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This calculator is for educational purposes. Double-check important results before acting on them.