URDB

Inductor Color Code Calculator

Decode inductor colour bands to an inductance value, with tolerance.

Example: Brown, Black, Brown, Silver is 100 µH (100 µH) ±10%.

Formula

L = (digits as a whole number) × multiplier, in microhenries

Calculations follow IEC 60062.

Worked example

Brown, Black, Brown, Silver is 100 µH (100 µH) ±10%.

  1. digits = band colours in order

    Brown = 1, Black = 0

    10

  2. L = digits × multiplier µH

    10 × 10 µH

    100 µH

  3. range = L ± tolerance

    100 µH ± 10%

    90 µH … 110 µH

Frequently asked questions

How do I read inductor colour bands?

Exactly like a resistor, except the answer is in microhenries. Two digit bands, a multiplier, then tolerance. Brown-black-brown is 10 × 10 = 100 µH — the same bands on a resistor would mean 100 Ω.

What does a gold multiplier band mean on an inductor?

×0.1 µH, so it marks sub-microhenry parts. Brown-black-gold is 10 × 0.1 = 1 µH. Silver is ×0.01. This mirrors how gold and silver work as resistor multipliers.

Why does the colour code not tell me the current rating?

There is no room for it, and no standard scheme. Saturation current, DC resistance and self-resonant frequency all matter more than the exact inductance in most designs, and all of them require the datasheet. The bands only give value and tolerance.

How can I tell an inductor from a resistor by looking at it?

Often you cannot with certainty, which is why they get mixed up. Inductors tend to be fatter with a more cylindrical body and sometimes a visible winding under the coating. A meter set to measure resistance settles it: an inductor reads close to zero ohms.

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