liminfoResistor Color Code
Free reference guide: Resistor Color Code
About Resistor Color Code
This Resistor Color Code Reference is a complete guide to identifying resistor values using the standard color band system. It documents all ten color digits (black through white) with their numeric values, multipliers from x1 to x1G, and tolerance designations. Gold and silver bands are covered for sub-ohm multipliers (x0.1 and x0.01) and common tolerance ratings of 5% and 10%.
The reference provides step-by-step reading instructions for 4-band (2 significant digits), 5-band (3 significant digits for precision resistors), and 6-band (with temperature coefficient) resistors. Standard value series are documented in full: E12 (12 values per decade, 10% tolerance), E24 (24 values, 5% tolerance), and E96 (96 values, 1% tolerance) with all standard values listed. SMD resistor markings are covered including 3-digit codes for E24 series, 4-digit codes for E96 series, and the EIA-96 two-digit-plus-letter encoding system.
Practical specifications include power rating tables for through-hole resistors (1/8W through 5W) and SMD packages (0201 through 2512), IEC 60063 tolerance grade letter codes from M (20%) down to A (0.05%), and temperature coefficient (TCR) calculations with typical values for carbon film, metal film, precision, and wirewound types. Common circuit application values are provided for I2C pull-ups, voltage dividers, LED current limiting, and current sense shunt resistors.
Key Features
- All 10 color band digit values with multipliers, tolerances, and temperature coefficients
- Step-by-step reading guides for 4-band, 5-band, and 6-band resistor identification
- Complete E12, E24, and E96 standard value series with all values listed per decade
- SMD marking decoding for 3-digit, 4-digit, and EIA-96 encoding systems
- Power rating tables for through-hole (1/8W to 5W) and SMD packages (0201 to 2512)
- IEC 60063 tolerance grade codes from 20% (M) through 0.05% (A) with band colors
- TCR calculation formula with typical ppm/C values for carbon, metal, precision, and wirewound resistors
- Common circuit values for I2C pull-ups, SPI, voltage dividers, LED limiting, and current sense resistors
Frequently Asked Questions
How do I read a 4-band resistor?
Orient the resistor so the tolerance band (gold or silver) is on the right side. Read left to right: the first two bands give significant digits (0-9 each), the third band is the multiplier (number of zeros), and the fourth band indicates tolerance. For example, Brown-Black-Red-Gold reads as 10 x 100 = 1k ohm with 5% tolerance.
What is the difference between 4-band and 5-band resistors?
A 4-band resistor has two significant digits and is typically 5% or 10% tolerance. A 5-band resistor has three significant digits and is used for precision resistors with 1% or better tolerance. The extra digit provides finer value resolution within the E96 series.
How do I decode a 3-digit SMD resistor code?
The first two digits are the significant value and the third digit is the multiplier (power of 10). For example, 103 means 10 x 10^3 = 10k ohm, and 472 means 47 x 10^2 = 4.7k ohm. An R in the code marks the decimal point position, so 4R7 equals 4.7 ohm. The code 000 or 0 indicates a 0 ohm jumper.
What are the E12, E24, and E96 series?
These are IEC 60063 preferred number series that define standard resistor values per decade. E12 has 12 values (1.0, 1.2, 1.5, ... 8.2) for 10% tolerance. E24 has 24 values for 5% tolerance and is the most commonly used series. E96 has 96 values for 1% precision resistors, with an adjacent value ratio of approximately 1.024.
What pull-up resistor value should I use for I2C?
For I2C standard mode at 100kHz, use 4.7k ohm. For fast mode at 400kHz, values between 2.2k and 4.7k ohm work well. The maximum recommended value is 10k ohm for slow speeds with short traces. Lower values provide stronger pull-up but increase current consumption.
How do I calculate voltage divider resistor values?
Use the formula Vout = Vin x R2 / (R1 + R2). Common combinations include R1=1.8k and R2=3.3k for 5V to 3.3V conversion (output approximately 3.24V), and R1=7k with R2=5k for 12V to 5V. Ensure the load impedance is much greater than R2, or add a buffer op-amp for accuracy.
What does the temperature coefficient (TCR) mean?
TCR measures how much a resistor value changes per degree Celsius, expressed in ppm/C. The formula is R(T) = R(25C) x [1 + TCR x (T-25) / 1,000,000]. Carbon film resistors have 200-500 ppm/C, metal film have 50-100 ppm/C, and precision types achieve 5-25 ppm/C. For a 10k ohm resistor with 100 ppm/C TCR, a 50 degree rise causes a 50 ohm (0.5%) change.
What value should I use for a current sense resistor?
The value depends on your current range: 10 milliohm for high current (10A+), 50 milliohm for medium current (1-5A), 100 milliohm for low current (up to 1A), and 1 ohm for micro-current measurement. Choose tolerance of 1% or better, TCR of 50 ppm/C or less, and a power rating at least 2x the expected I-squared-R dissipation.