Inductor Color Code Calculator
This inductor color code calculator reads the four-band color code printed on a molded inductor and returns the inductance in microhenries. The color bands follow the same scheme as resistors: the first two bands give the significant digits and the third band gives the power-of-ten multiplier, with a fourth band for tolerance. Each color maps to a number from 0 for black through to 9 for white, the standard sequence the US National Institute of Standards and Technology and electronics references use. Enter the numeric value of the first digit band, the second digit band and the multiplier band (the power of ten), and the calculator combines them as the two-digit significant figure multiplied by ten raised to the multiplier. It reports the result in microhenries and also converts to millihenries and henries so you can read off the value in whatever unit suits the circuit. Use it to identify an unmarked coil, check a salvaged part, or teach the code. The same black-through-white sequence from resistors applies here, only the result is read in microhenries. Every figure is computed deterministically from the color code formula shown in full below, with a worked example that reconciles exactly to the calculator so you can follow each step yourself.
The first two bands are the digits and the third is the power-of-ten multiplier: brown (1), black (0), red (x10^2) gives 10 x 100 = 1,000 microhenries, equal to 1.00 millihenry. Inductors read exactly like resistors in microhenries.
Inductor color code formula
L = ( d1 x 10 + d2 ) x 10 ^ multiplier microhenries
d1 = first significant digit (first band)
d2 = second significant digit (second band)
multiplier = power of ten (third band)
The color sequence black, brown, red, orange, yellow, green, blue, violet, grey, white maps to 0 through 9. The first two bands form a two-digit number; the third band scales it by a power of ten, exactly as on a resistor, but the result is read in microhenries.
Worked example
Read an inductor banded brown, black, red: first digit 1, second digit 0, multiplier 2.
- two-digit value = 1 x 10 + 0 = 10
- multiplier = 10 ^ 2 = 100
- L = 10 x 100 = 1,000 microhenries
- 1,000 microhenries = 1.00 millihenry = 0.001000 henry
The inductance is 1,000 microhenries, equal to 1.00 millihenry. These are the calculator's default inputs, so the result above matches the widget exactly.
Color to value mapping
Each color band corresponds to a digit and, in the third position, a power-of-ten multiplier.
| Color | Digit | Multiplier |
|---|---|---|
| Black | 0 | x1 |
| Brown | 1 | x10 |
| Red | 2 | x100 |
| Orange | 3 | x1,000 |
| Yellow | 4 | x10,000 |
| Green | 5 | x100,000 |
Color code and measurement reference: US National Institute of Standards and Technology (NIST).
Inductor Color Code Calculator: frequently asked questions
What unit are inductor color codes in?
The four-band color code reads directly in microhenries, abbreviated uH. So a value of 1,000 from the code means 1,000 microhenries, which equals 1 millihenry. This differs from the resistor code only in the unit; the digit and multiplier scheme is identical.
How do I convert a color to a number?
Use the standard sequence: 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 read as digits and the third as the power of ten. Enter those numbers into the calculator rather than the color names.
What does the fourth band mean?
The fourth band is the tolerance, how far the real inductance may stray from the nominal value. Silver is typically 10 percent and gold 5 percent, while a missing fourth band implies 20 percent. Tolerance does not change the nominal value this calculator reports; it tells you the expected spread around it.
Why are some inductors marked differently?
Small surface-mount and precision inductors often use printed numeric codes or direct values instead of color bands, and some use a gold or silver third band to denote a fractional multiplier. This calculator covers the common four-band molded inductor where the third band is a whole-number power of ten.
How do I read the bands in the right order?
Hold the inductor so the tolerance band, usually wider or gold or silver, is on the right. Then read from the left: first digit, second digit, multiplier, tolerance. If the body is symmetric, the tolerance color (gold or silver) tells you which end is the last band.
Official sources
- Electrical units and measurement reference: US National Institute of Standards and Technology (NIST). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.