Inductor (Coil) Color Code Calculator (Colors → Inductance & Inductance → Colors)
Calculate the inductance and tolerance of a small inductor (coil) from its 3 or 4 color bands, shown in µH, mH, and H. You can also enter an inductance value to look up the matching color bands.
Color band reference table
| Color | Digit | Multiplier (µH) | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | — |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1,000 | ±3% |
| Yellow | 4 | ×10,000 | ±4% |
| Green | 5 | ×100,000 | — |
| Blue | 6 | ×1,000,000 | — |
| Violet | 7 | ×10,000,000 | — |
| Gray | 8 | ×100,000,000 | — |
| White | 9 | ×1,000,000,000 | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
| No band (unmarked) | — | — | ±20% |
What Is an Inductor Color Code? Reading Inductance from Color Bands
Small inductors (coils) print several color bands on the body, just like resistors do, to represent numeric values in color. With three bands, you get two digits plus a multiplier; with four bands, a tolerance band is added on top of that, letting you read off an inductance value in µH (microhenries). The digit colors themselves (black=0 through white=9) are shared with the resistor color code, but two things trip people up: the multiplier's unit is µH rather than Ω, and the tolerance band's color-to-percent mapping is its own distinct scheme, different from resistors.
This tool covers both directions: a "Colors → Inductance" mode that calculates the inductance value and tolerance from a chosen set of color bands, and an "Inductance → Colors" mode that works backward from a target inductance to the standard band sequence. It is built to help whether you are peering at a tiny part on a circuit board with a loupe or magnifier, or hunting for a specific value during the design stage.
How to Read an Inductor Color Code
- Choose a calculation mode Pick "Colors → Inductance" if you want to find the inductance from the bands on a part in hand, or "Inductance → Colors" if you already know the target value and want to find the matching bands.
- Select the 1st and 2nd digit band colors Treat the end with the wider gap as the right-hand side, then choose the 1st and 2nd digit colors from the dropdowns, reading left to right.
- Select the multiplier band color Choose the color of the third band. This determines the power of ten the digits are multiplied by, giving a result in µH.
- Select the tolerance band color (4-band parts only) If a fourth band is present, select its color too. On 3-band parts where this band is omitted, the tolerance defaults to ±20% by convention.
- Check the calculated result The inductance value and its tolerance range are displayed in µH, mH, and H so you can read whichever unit suits your part.
Tips for getting more out of it
- Inductor color codes reuse the same digit and multiplier colors as resistors, but the unit is µH (microhenries), not Ω. Brown-black-red-gold reads as 1kΩ on a resistor, but as 1000µH (1mH) on an inductor.
- A 3-band inductor omits the tolerance band, which is treated as ±20% by convention. If a 4th band is present, select its color to see the exact tolerance.
- The tolerance band color-to-percent mapping differs from resistors: orange=±3%, yellow=±4%, and black=±20% are specific to inductors, so reusing the resistor tolerance table will give the wrong answer.
- If the "Inductance → Colors" mode finds no match, the value you entered likely does not round cleanly to 2 significant figures. Try rounding to the nearest standard value.
- RF chokes and power-line noise-suppression inductors are often marked with small values (a few µH to a few hundred µH), so entering the value in µH first tends to be the easiest to read.
When This Tool Comes in Handy
Identifying an unknown coil on a board
When you cannot make out the part number on a small inductor used in a power supply or noise-suppression circuit, entering its color bands lets you pin down the inductance value as a starting point for repair or analysis.
Choosing a part during design
If you already know the inductance you need for a DC-DC converter or an RF filter, the "Inductance → Colors" mode shows you the band sequence to look for when browsing catalogs or shelves at a component shop.
Checking incoming stock
When you have bought a batch of inductors from an overseas supplier, reading the color bands lets you verify that what arrived actually matches the values in your order.
Learning the code in class or in the lab
Students studying electronics can use real examples to see how the inductor's color-to-percent mapping differs from the resistor code they may already know.
Glossary
- Inductance
- A measure of how strongly a coil resists changes in current flowing through it, measured in henries (H). Small components are usually specified in mH (one-thousandth of a henry) or µH (one-millionth of a henry).
- Color band
- A colored stripe printed on the body of an inductor or resistor to represent a numeric value. Separate bands are used for the digits, the multiplier, and the tolerance.
- Multiplier band
- The band that comes after the digit bands, indicating the power of ten to multiply the preceding one or two digits by. On an inductor, the resulting value is expressed in µH.
- Tolerance
- How far the actual inductance may deviate from the labeled value. It is shown by the fourth band's color; when that band is absent, the tolerance is conventionally assumed to be ±20%.
- RF choke coil
- An inductor used to attenuate radio-frequency (RF) noise while letting DC or low-frequency signals pass through. It is also widely used to suppress noise on power lines.
- JIS/EIA standards
- JIS is Japan's industrial standard, and EIA is a standard set by the American Electronics Industries Alliance. Inductor color codes have never been unified under a single international standard, so the exact mapping can vary slightly between reference sources.
Frequently asked questions
Side Note — Why coils borrow the same color language as resistors
Small inductors (coils) are often built as cylindrical parts that look a lot like resistors, and they face the same tight constraints on printing space. As a result, the "represent digits with color" scheme established for resistors was carried over directly, reusing the same sequence from black=0 through white=9. The physical quantity being represented is different, though — µH (inductance) rather than Ω (resistance) — so a reader who does not recognize that a part is a coil rather than a resistor can easily misread the value by orders of magnitude.
The subtly different tolerance-band color mapping has also long been a source of confusion for practitioners. Resistors use high-precision colors such as green=±0.5%, blue=±0.25%, and violet=±0.1%, while inductors commonly use orange=±3%, yellow=±4%, and black=±20% — assignments that do not appear on the resistor chart at all. This stems from resistors and inductors being standardized somewhat independently by industry groups over time, rather than from a single unified international standard; several references describe broadly similar but not identical conventions.
Small inductors quietly do a lot of work in places that are easy to overlook — RF tuning and filtering circuits, and choke coils used to suppress noise on power lines, to name two common examples. On a crowded board they can be hard to spot among capacitors and resistors, and in field work where direct measurement or datasheet lookup is not practical, reading the color bands is sometimes the only clue available. This tool is meant to sit alongside the resistor color code calculator and the capacitor code converter in the same electricity subcategory, together covering the common task of reading markings on passive components.