Decode Any 4-Band Resistor
Last reviewed: January 2026
A resistor color code calculator decodes the colored bands on a resistor to determine its resistance value and tolerance. It supports 4-band, 5-band, and 6-band resistors, and can also work in reverse — entering a resistance value to find the corresponding color bands.
Resistors use colored bands to indicate their resistance value in ohms. A standard 4-band resistor has two digit bands, one multiplier band, and one tolerance band. Read from the band closest to one end: the first two bands give digits, the third gives the number of zeros to add.[1] For example, brown-black-red-gold = 10 × 100 = 1,000Ω (1KΩ) ±5%. The mnemonic "Bad Boys Race Our Young Girls But Violet Generally Wins" helps remember the order: Black(0), Brown(1), Red(2), Orange(3), Yellow(4), Green(5), Blue(6), Violet(7), Grey(8), White(9).[2] Five and six-band resistors add precision: the extra band provides a third significant digit, and the tolerance band uses tighter specifications (brown = ±1%, red = ±2%).[3] Use the Ohm's Law Calculator to apply resistance values in circuit calculations.
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | — |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1K | — |
| Yellow | 4 | ×10K | — |
| Green | 5 | ×100K | ±0.5% |
| Blue | 6 | ×1M | ±0.25% |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
Resistor color codes are a standardized system for marking resistance values on through-hole resistors using colored bands painted on the component body. The system was developed because resistors are too small for printed numbers to be legible, and the bands can be read regardless of the component's orientation on a circuit board. Standard resistors have 4 bands, precision resistors have 5 bands, and some ultra-precision resistors have 6 bands. The color sequence represents digits and multipliers using the same base code: Black=0, Brown=1, Red=2, Orange=3, Yellow=4, Green=5, Blue=6, Violet=7, Grey=8, White=9. The final band indicates tolerance — the acceptable deviation from the marked value. For related electrical calculations, see our Power Calculator.
| Color | Digit Value | Multiplier | Tolerance Band |
|---|---|---|---|
| Black | 0 | ×1 (10⁰) | — |
| Brown | 1 | ×10 (10¹) | ±1% |
| Red | 2 | ×100 (10²) | ±2% |
| Orange | 3 | ×1K (10³) | ±0.05% |
| Yellow | 4 | ×10K (10⁴) | ±0.02% |
| Green | 5 | ×100K (10⁵) | ±0.5% |
| Blue | 6 | ×1M (10⁶) | ±0.25% |
| Violet | 7 | ×10M (10⁷) | ±0.1% |
| Grey | 8 | ×100M (10⁸) | ±0.01% |
| White | 9 | ×1G (10⁹) | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
For a 4-band resistor, the first two bands are digit values, the third band is the multiplier, and the fourth band is tolerance. A resistor with Brown-Black-Red-Gold bands reads as: 1 (Brown), 0 (Black) × 100 (Red) = 1,000 ohms (1 kΩ) with ±5% tolerance (Gold). This means the actual resistance falls between 950Ω and 1,050Ω. For 5-band precision resistors, the first three bands are digits, the fourth is the multiplier, and the fifth is tolerance. A resistor with Brown-Black-Black-Brown-Brown reads as 1 (Brown), 0 (Black), 0 (Black) × 10 (Brown) = 1,000 ohms with ±1% tolerance (Brown) — the same nominal value but guaranteed to be between 990Ω and 1,010Ω.
The trickiest part of reading resistor color codes is determining which end to start from. The tolerance band (typically gold, silver, or a distinctly spaced band) should be on the right side. If the resistor has no tolerance band, it has ±20% tolerance (rarely seen in modern components). When bands are ambiguous, consider that standard resistance values follow the E-series: E12 values (10% tolerance) include 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, and 82 with their multiples. If your reading doesn't match an E-series value, you may be reading the bands in the wrong direction. Many hobbyists and professionals use mnemonic devices to remember the color order — the most commonly taught is "Bad Beer Rots Our Young Guts But Vodka Goes Well," though digital tools and apps have made memorization less essential.
Resistors are the most fundamental passive component in electronics, controlling current flow, dividing voltage, setting bias points for transistors, limiting LED current, and creating timing circuits. Ohm's Law — V = I × R (voltage equals current times resistance) — governs how resistors behave in circuits. A 330Ω resistor in series with an LED connected to 5V limits current to approximately (5V - 2V) / 330Ω = 9.1 mA, protecting the LED from overcurrent damage. Power dissipation in a resistor is P = I²R or P = V²/R — exceeding a resistor's power rating (typically ¼W for standard through-hole resistors) causes overheating, discoloration, and eventual failure.
Series and parallel resistor combinations are essential circuit building blocks. Resistors in series add directly: R_total = R1 + R2 + R3. Resistors in parallel combine reciprocally: 1/R_total = 1/R1 + 1/R2 + 1/R3. For two parallel resistors, the simplified formula R_total = (R1 × R2) / (R1 + R2) is particularly useful. Voltage dividers — two resistors in series — produce an output voltage proportional to the ratio of the resistances: V_out = V_in × R2 / (R1 + R2). This simple circuit is used throughout electronics for level shifting, sensor interfaces, and reference voltages. For more complex circuit calculations, see our Scientific Notation Calculator for working with component values and our Unit Converter for unit conversions.
Surface-mount device (SMD) resistors — the tiny rectangular components used in modern electronics — use numerical codes instead of color bands because their bodies are too small for colored stripes. The most common system uses three digits: the first two are significant digits and the third is the multiplier (number of zeros). A code of "472" means 47 × 10² = 4,700Ω (4.7 kΩ). Precision SMD resistors use four digits: "4701" means 470 × 10¹ = 4,700Ω. The code "R" indicates a decimal point: "4R7" means 4.7Ω, and "R47" means 0.47Ω. Zero-ohm resistors (marked "000" or just "0") are used as jumper wires on circuit boards.
Common SMD package sizes include 0402 (1.0 × 0.5mm), 0603 (1.6 × 0.8mm), 0805 (2.0 × 1.25mm), and 1206 (3.2 × 1.6mm). The trend toward smaller packages continues as electronics miniaturize, with 0201 (0.6 × 0.3mm) components becoming common in smartphones and wearables. These components are essentially invisible to the naked eye and require automated assembly equipment. For hobbyists and prototypers, 0805 and 1206 sizes are the smallest that can be practically hand-soldered. Resistor values are available in standard E-series: E12 (±10% tolerance, 12 values per decade), E24 (±5%, 24 values), E96 (±1%, 96 values), and E192 (±0.5%, 192 values). Most hobbyist kits include the E12 or E24 series, which cover the vast majority of common applications.
Beyond standard fixed resistors, several specialty types serve specific functions. Potentiometers (variable resistors) allow manual resistance adjustment and are used in volume knobs, brightness controls, and calibration circuits. Thermistors change resistance with temperature — NTC thermistors decrease resistance as temperature rises and are used in temperature measurement and compensation circuits. Light-dependent resistors (LDRs or photoresistors) decrease resistance when exposed to light, enabling automatic lighting controls and light-sensing applications. Fuses are essentially resistors designed to fail at a specific current level, protecting circuits from overcurrent damage.
The tolerance band indicates how much the actual resistance may deviate from the labeled value. Gold = ±5%, silver = ±10%, brown = ±1%, and red = ±2%. For most hobby and prototyping circuits, 5% tolerance is perfectly adequate. Precision circuits (audio equipment, measurement instruments, feedback networks) require 1% or better, and these resistors use a 5-band color code for more digits of precision. Surface-mount resistors (SMD) use a numeric code instead of colors — "472" means 47 × 10² = 4,700Ω. When selecting resistors, also consider power rating (¼W standard for signal circuits, higher for power applications) and temperature coefficient. Design your LED circuits with our LED Resistor Calculator.
→ Check your units. Science calculations are unit-sensitive. Make sure all inputs use the same system (SI or Imperial) to avoid conversion errors.
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→ Explore the relationships. Change one variable at a time to see how it affects the result. This builds physical intuition about the underlying principles.
See also: Ohm's Law Calculator · LED Resistor Calculator · Electrical Power Calculator