Resistor color bands

The colored bands on resistors indicate their resistance value and tolerance, following an internationally standardized code essential for electronics.

About this subject

Resistors are passive components that limit electric current in circuits. Their colored bands, usually 4 or 5, form a color code indicating the resistance value in ohms. Each color corresponds to a numeric digit, as standardized by IEC 60062. The first two bands represent significant digits, the third is the multiplier (power of 10), and the fourth indicates tolerance (precision). In 5-band resistors, the first three are digits, the fourth is the multiplier, and the fifth is tolerance.

The color code was developed in the early 20th century to facilitate reading values on small components. Common colors: black (0), brown (1), red (2), orange (3), yellow (4), green (5), blue (6), violet (7), gray (8), white (9). For the multiplier, silver (0.01) and gold (0.1) also appear. Tolerance is indicated by gold (±5%), silver (±10%), brown (±1%), among others. Wire-wound or SMD resistors may use alphanumeric markings, but the band code remains predominant for through-hole components.

Knowing how to interpret these colors is fundamental for technicians and engineers, as a wrong resistor value can compromise an entire circuit. Reading is done from left to right, with the tolerance band usually spaced farther apart or having a wider gap. Online calculators and apps facilitate decoding. The body color of the resistor may also indicate power rating, but this is not part of the band code. Modern resistors offer precision up to 0.01% tolerance in high-accuracy components.

Interestingly, the color code is so widespread that it has inspired mnemonics in English, such as 'Bad Boys Run Over Yellow Grass But Vicious Grey Wolves' to remember the sequence. Standardization ensures that resistors from different manufacturers are interchangeable as long as they meet the same specification. However, with the advancement of SMD technology, miniature resistors now use three- or four-digit codes, but the colored band system remains the most educational and recognized method.

Frequently Asked Questions

How to read a 4-band resistor?

Hold the resistor with the tolerance band (usually gold or silver) to the right. The first two bands on the left are digits, the third is multiplier. Example: brown (1), black (0), red (100) = 10 × 100 = 1000 ohms (1 kΩ).

What is the order of colors in resistor color code?

The increasing order from 0 to 9 is: black, brown, red, orange, yellow, green, blue, violet, gray, white. For multipliers, silver (×0.01) and gold (×0.1) are also common.

What does the tolerance band on a resistor mean?

It indicates the accuracy of the actual value relative to the nominal. Gold: ±5%, silver: ±10%, brown: ±1% (for 5-band resistors). Lower percentage means higher precision.