Resistor Color Code Calculator

Resistor Color Code Decoder

Select band type and choose colors from the dropdowns below. The resistor visual and calculated value update live.

Reverse Lookup Value to Color Bands

Enter a resistance value and see the corresponding color code bands.

SMD Resistor Code Decoder

Decode 3-digit, 4-digit, and EIA-96 SMD resistor codes. Enter the code printed on the component.

SMD Code Quick Reference

EIA-96 Multiplier Letters

Series & Parallel Resistor Calculator

R_total = R1 + R2 + R3 +. (current is same, voltage divides)

E-Series Standard Resistor Values

Standard preferred values that repeat in each decade. Manufacturers produce only these values, spaced logarithmically so tolerance bands overlap to cover all possible resistance targets.

E12 Series (10% Tolerance)

12 values per decade. Used with gold tolerance band.

E24 Series (5% Tolerance)

24 values per decade. Most common for general electronics.

E96 Series (1% Tolerance)

96 values per decade. Precision applications.

E-Series Comparison

Resistor Power Rating Guide

Choose the right power rating based on the heat your resistor needs to dissipate. Always derate by at least 50% for reliability.

Through-Hole Resistor Power Ratings

SMD Resistor Power Ratings

Power Calculation Quick Reference

To find the power dissipated by a resistor, use any of these equivalent formulas:

Complete Color Code Reference

Full reference table showing the meaning of each color in every band position.

How to Read Resistor Color Codes

Understanding the Resistor Color Code System

The resistor color code system was developed in the 1920s by the Radio Manufacturers Association (RMA) as a way to mark small components that were too tiny for printed numbers. Each colored band represents a specific digit, multiplier, or tolerance value. The system is still used today on through-hole resistors, even though SMD resistors now use printed numeric codes.

Reading a 4-Band Resistor

A 4-band resistor is the most common type. Orient the resistor so the tolerance band (gold or silver) is on the right side. The tolerance band typically has a slightly larger gap from the nearest band. Band 1 (leftmost) is the first significant digit. Band 2 is the second significant digit. Band 3 is the multiplier (how many zeros to add). Band 4 is the tolerance. For example, a resistor with Brown-Black-Red-Gold bands reads as: 1, 0, ×100 = 1000Ω (1kΩ) with ±5% tolerance.

Reading a 5-Band Resistor

A 5-band resistor adds a third significant digit for more precision. These are typically 1% tolerance (brown tolerance band) or better. Band 1 is the first digit, Band 2 the second, Band 3 the third significant digit, Band 4 is the multiplier, and Band 5 is tolerance. A 5-band Brown-Red-Black-Brown-Brown reads as: 1, 2, 0, ×10 = 1200Ω (1.2kΩ) with ±1% tolerance.

Reading a 6-Band Resistor

A 6-band resistor adds a temperature coefficient band, indicating how much the resistance changes with temperature in parts per million per degree Celsius (ppm/°C). This sixth band is typically brown (100 ppm/°C) for standard metal film resistors. Precision components may use blue (10 ppm/°C) or violet (5 ppm/°C). The temperature coefficient is critical in precision measurement circuits, oscillators, and instrumentation where temperature stability matters.

Common Mnemonics for Remembering Color Codes

A widely used mnemonic to remember the color sequence (Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Gray, White) is: "Big Beautiful Roses Occupy Your Garden But Violets Grow Wild." Each first letter corresponds to a color: B="Black" (0), B="Brown" (1), R="Red" (2), O="Orange" (3), Y="Yellow" (4), G="Green" (5), B="Blue" (6), V="Violet" (7), G="Gray" (8), W="White" (9). With practice, most engineers memorize the codes directly from frequent use.

Identifying Resistor Orientation

Determining which end to start reading from can be confusing, especially for beginners. Here are reliable methods: First, the tolerance band (gold, silver, or a wider gap) is always on the right. Second, for 4-band resistors, the first band is usually closer to one end of the body. Third, black is never a first band (it would be meaningless as a leading zero). Fourth, for 5 and 6-band resistors, look for the group of bands that are closer together on one side, and start reading from that side.

Browser Compatibility

I've tested this resistor calculator across all major browsers. The calculator uses standard JavaScript DOM operations and CSS styling that are universally supported. The color band visualization renders identically across all tested platforms.

Frequently Asked Questions

How to Use This Resistor Calculator

Step 1 Choose Your Band Count

Select whether your resistor has 4, 5, or 6 color bands using the tabs at the top of the calculator. Count the bands carefully. If you see a metallic band (gold or silver) on one end, that is the tolerance band and goes on the right. Standard carbon film resistors usually have 4 bands. Metal film precision resistors typically have 5 bands.

Step 2 Select Colors for Each Band

Use the dropdown menus to select the color for each band, reading from left to right. The visual resistor above the dropdowns updates in real time, showing you exactly what the resistor looks like. This helps you verify that you are reading the colors in the correct order.

Step 3 Read the Calculated Value

The resistance value, tolerance, and (for 6-band) temperature coefficient are displayed below the dropdowns. The value is shown in the most readable unit (ohms, kilohms, or megaohms). The min/max range based on tolerance is also shown so you know the actual expected range of the component.

Using Reverse Lookup

If you know the resistance value and find the color bands, scroll down to the Reverse Lookup section. Enter the value, select the unit and band count, then click Find Colors. The tool will show you the exact band colors and display them on a visual resistor diagram.