Resistor Color Code Calculator

A bidirectional tool to calculate resistance from color bands or find color bands from a value.
Fully supports 4/5/6 bands and SMD (3/4 digits).

🔄

Bidirectional

Convert from color to value, and value to color

📏

IEC Compliant

Accurate calculations based on IEC 60062/60063

👁️

Color-blind Support

Text labels provided alongside colors

Calculation Result

---

about,

About

This is a free online tool to calculate resistor color codes and SMD (Surface Mount Device) codes intuitively in your browser. It fully supports 4-band, 5-band, and 6-band resistors, providing accurate values based on the international standard IEC 60062:2016.

To support color vision accessibility, the tool is designed not to rely solely on color. Text labels such as "Brown (1)" are always displayed alongside colors, ensuring usability in grayscale environments or for those with color vision deficiency. If you are interested in color blindness simulation, you can also use our Color Blind Simulator.

how to use,

How to Use

Find value from color (Forward)

Using 4/5/6 Band Modes

Select the number of bands (4 to 6) from the top tabs. Simply choose the color bands painted on your resistor in order from the dropdowns on the left, and the resistance value (Ω, kΩ, MΩ, etc.), tolerance, and temperature coefficient will be displayed instantly on the right.

Find color from value (Reverse)

Using Reverse / SMD Modes

Select the "Reverse Lookup" tab, input your desired resistance (e.g., 4700) and unit (Ω/kΩ), and the corresponding color bands will be drawn on the screen. If you enter a non-standard value, the closest standard E24 value will also be suggested. In the "SMD" tab, you can read the resistance from the 3- or 4-digit code printed on the board.

glossary,

Glossary

Significant Figures: The first few color bands of the code that represent the numerical value itself. For 4-band resistors, the first two bands are significant figures; for 5-band and 6-band resistors, it's the first three bands. For example, "Brown, Black" represents "1, 0", so the significant figures are "10".
Multiplier: The band that indicates the "power of 10" to multiply the significant figures by. It is placed after the significant figures (the 3rd band for 4-band, 4th for 5/6-band). Examples include Red (×100) or Gold (×0.1), and it plays a crucial role in determining the final number of digits for the resistance.
Tolerance: The band indicating the possible error range (±%) by which the actual resistance may vary from the nominal value due to manufacturing tolerances. It is usually placed at the end or second to last. Common ones are Gold (±5%) for general use, and Brown (±1%) for precision use.
Temperature Coefficient of Resistance (TCR): The value indicated by the last band of a 6-band resistor, showing how much the resistance varies in ppm/K when the temperature changes by 1°C (or 1K). It is an essential metric for calculating the effects of temperature changes in precision instruments or circuits operating in harsh environments.
SMD (Surface Mount Device): Ultra-small resistors that do not have wire leads and are soldered directly onto the surface of a PCB. Since they are too small for color bands, they have 3- or 4-digit codes printed on them, such as "472". The first digits represent the significant figures, and the last digit represents the multiplier (number of zeros).

faq,

FAQ

What if the colors are faded or hard to tell apart?

Heat and age can cause resistor color bands to fade, making it difficult to distinguish between red and brown, or violet and blue. Since this tool includes text labels for each color (e.g., "Brown (1)"), you can try the possible color combinations and see which one results in a standard value (like the E24 series) to make an educated guess.

Can I input any arbitrary value for reverse lookup?

Yes, you can. However, since resistors are not manufactured for every single numerical value, the tool will automatically calculate and display the closest standard resistance value from the IEC 60063 E24 series for any arbitrary input.

Is the EIA-96 code for SMD resistors supported?

The current version supports the most common 3-digit and 4-digit SMD code calculations. Code conversion based on alphanumeric lookup tables like the EIA-96 standard (e.g., 01C = 10kΩ) is planned for a future update.

What does the last color band on a 6-band resistor mean?

The 6th band represents the "Temperature Coefficient of Resistance (TCR)" in units of ppm/K. This indicates how much the resistance value will change with ambient temperature variations, which is a crucial metric for precise circuit design.

How are the calculation results verified?

The calculation logic of this tool fully complies with the international standard IEC 60062:2016 (Marking codes for resistors and capacitors). During development, we conducted strict bidirectional testing using numerous test cases (e.g., Yellow-Violet-Red-Gold = 4.7kΩ±5%).

use cases,

Use Cases

🛠️
Electronics & DIY
Quickly verify the value of a resistor you have on hand for electronics projects with Arduino or Raspberry Pi. Accurately calculate the correct value from color bands.
📚
Engineering Education
Useful as a supplementary tool for electrical and electronic engineering students at technical schools or universities to learn and check how to read color codes.
🔧
Circuit Repair & Maintenance
Helpful when repairing old circuit boards to deduce the value of burnt or faded resistors based on the remaining visible color bands.
🔍
Sorting SMD Components
Convenient for sorting SMD resistors for PCB assembly or quickly determining the resistance from the tiny text printed on the chips.