Reading inductor bands
Moulded inductors use the same colours as resistors: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. The first two bands are digits, the third is the multiplier, and the fourth the tolerance, all in microhenries. So brown, black, brown is 10 × 10 = 100 µH. Gold as a multiplier means × 0.1 and silver × 0.01, so red, red, gold is 2.2 µH.
Some inductors use a wide silver band at one end to show the military-style marking, and others print the value as numbers instead, such as 101 for 100 µH, using the same scheme as SMD codes. The SMD code calculator reads those.
Check before you trust it
Inductors and resistors can look very similar. An inductor usually reads a low resistance on a meter, often under a few ohms, and many are slightly fatter in the middle. An LCR meter or NanoVNA confirms the value. For resistor bands, use the resistor colour code calculator.
Questions
What unit are inductor colour codes in?
Microhenries (µH).
What is brown, black, brown on an inductor?
100 µH.
What is red, red, gold on an inductor?
2.2 µH. Gold as the multiplier means × 0.1.
How do I tell an inductor from a resistor?
Measure it. An inductor shows a very low resistance, usually a few ohms or less.