Resistor Color Code Calculator (Color to Value & Value to Color)

Calculate resistance and tolerance from a resistor's color code (4-band or 5-band). You can also enter a resistance value to find the matching band colors.

Last updated: 2026-09-17

What the Resistor Color Code Means

The colored bands printed on a resistor are a compact way of encoding its resistance value and tolerance without printing numbers directly on the tiny component. Each color stands for a digit from 0 to 9. Reading from left to right, the first bands give the significant digits (two for a 4-band resistor, three for a 5-band resistor), followed by a multiplier band, and finally a tolerance band. Because the number of significant digits depends on how many bands the resistor has, counting the bands correctly is always the first step before decoding the colors.

This tool covers both directions of that process: the "Color to Value" mode lets you pick the colors you see on a physical resistor to find its resistance and tolerance range, while "Value to Color" works backward from a resistance value you already know or need, returning the standard band sequence that represents it. Together they help you both identify unknown components and confirm what to look for before buying or soldering a part.

How to Use This Tool

Choose a calculation mode Pick "Color to Value" to read a physical resistor, or "Value to Color" to look up the colors for a resistance you already know.
Select the number of bands Count the bands on the resistor (4 or 5) and select the matching option; this determines how many input fields appear.
Enter the colors or the value In "Color to Value" mode, choose each band's color from the dropdowns. In "Value to Color" mode, enter the resistance, unit, and tolerance.
Read the result The resistance and tolerance range, or the matching color sequence, updates instantly as you change the inputs.
Cross-check with a measured value If you're unsure about a color, measure the resistor with a multimeter and enter that value in the opposite mode to confirm.

Tips for getting more out of it

When holding a real resistor, orient it so the tolerance band (usually gold or silver) is on the right and read from the left. The band with the widest gap before it is the tolerance band.
The difference between 4-band and 5-band codes is the number of significant digits. Common carbon-film resistors use 4 bands, while precision metal-film resistors use 5 bands and often have tolerances of ±1% or tighter.
If the "Value to Color" mode can't find matching colors, the value may not fall on the standard E12/E24 series, or the tolerance you entered isn't one of the standard percentages (±1/2/5/10/20% etc.).
Gold and silver are used both as multiplier colors (×0.1 and ×0.01) and tolerance colors (±5% and ±10%), so the same color means something different depending on its position.
If the bands are hard to read in dim light or on a faded resistor, measure the resistance with a multimeter and enter that value into "Value to Color" mode to cross-check the expected color sequence.

Common Use Cases

Selecting parts for a project

Quickly match a schematic's required resistance value to the physical part by checking its color bands before soldering it in.

Sorting old component stock

Identify the value of unlabeled or unmarked resistors pulled from a parts bin, using only the visible color bands.

Learning electronics fundamentals

Students and instructors can work through concrete examples to understand how the color code system encodes digits and tolerance.

Checking colors before ordering

Confirm what band sequence to expect for a specific resistance value before placing an order from an online parts supplier.

Finding replacement parts for repairs

Read the value of a resistor on a failed circuit board from its bands to find a matching replacement part.

Glossary

Tolerance: The percentage by which the actual resistance may deviate from the labeled value. Each color corresponds to a fixed tolerance, such as gold for ±5%, silver for ±10%, or brown for ±1%.
Multiplier band: The band that indicates the power of ten to multiply the significant digits by. For example, black means ×1 and red means ×100.
E12 and E24 series: Standardized sets of resistance values used in commercial manufacturing. E12 has 12 logarithmically spaced values per decade and E24 has 24; resistors with values outside these series are not sold.
Temperature coefficient: A measure of how much a resistor's value shifts as ambient temperature changes. Some 6-band precision resistors add an extra band to indicate this coefficient.
Carbon-film resistor: The most common type of resistor, made from a thin carbon film. It is inexpensive and widely available, typically with a looser tolerance around ±5%.
Metal-film resistor: A precision resistor made from a thin metal film. It is manufactured to tighter tolerances than carbon-film types, often ±1% or better on 5-band parts.

Frequently Asked Questions

Resistors are tiny components, and printed numbers become hard to read once the part is mounted, oriented differently, or dirty with age. Colored bands remain legible even on small parts from a distance, which is why the Radio Manufacturers Association (RMA, now the EIA) standardized the color code system in the 1920s.

5-band resistors are generally more precise. A 4-band code can only express two significant digits, while a 5-band code expresses three, which is why precision metal-film resistors with tolerances of ±1% or tighter typically use 5 bands.

By convention, a missing tolerance band means ±20%. This is mostly seen on older or very inexpensive general-purpose resistors; most parts sold today include an explicit gold, silver, or brown tolerance band instead of leaving it blank.

Lighting color temperature and gradual discoloration of the resistor surface can make bands hard to distinguish. If possible, measure the resistance with a multimeter and use the "Value to Color" mode to work backward from the measured value.

Side Note — The Color Code Follows the Order of the Rainbow

The resistor color code traces back to a standard set by the Radio Manufacturers Association (RMA, now the EIA) in the United States in the 1920s. During the vacuum-tube radio era, resistors were shrinking too small to print numbers on, so colored paint bands were adopted instead. The sequence from black (0) to white (9) roughly follows the wavelength order of visible light, from low-energy red tones to high-energy violet and white, which is widely believed to have made the scheme easier for engineers of the time to memorize.

A static table of resistor colors is easy to find with a quick search, but actually picking the colors you see on a real resistor to look up its value — or working backward from a desired resistance to the colors that represent it — is something a plain table can't do on its own. Sites like dCode and Digi-Key are well known as go-to conversion tools in the electronics hobbyist world, making the "color code calculator" one of the most classic tool categories in the space. Alongside the Ohm's law calculator in the same physics category, this tool rounds out the basic circuit-design calculations on the site.

Commercial resistors aren't sold at arbitrary values; they follow standardized series such as E12 (12 logarithmically spaced values like 10, 12, 15, 18, 22... multiplied by powers of ten) or the finer E24 series. The "Value to Color" mode in this tool simply rounds your input to the required number of significant digits and works backward from there, so entering a value outside the E12/E24 series may produce a color combination that doesn't correspond to any resistor actually sold.

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