Resistor Color Code Calculator

Como ler um resistor?

Resistores axiais têm 4, 5 ou 6 faixas coloridas. As primeiras (2 ou 3) são dígitos significativos, a seguinte é o multiplicador, depois vem a tolerância e (em 6 faixas) o coeficiente de temperatura.

Para ler na ordem correta: a faixa mais próxima de uma das pontas é a primeira. A faixa de tolerância (geralmente dourada ou prateada) costuma ficar isolada da última faixa de valor.

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Resistor color code: EIA standard

The resistor color code follows the EIA (Electronic Industries Alliance) standard. A 4-band resistor uses two digits + multiplier + tolerance; a 5-band resistor uses three digits + multiplier + tolerance (precision parts); a 6-band resistor adds a temperature coefficient. Digit colors: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, gray 8, white 9. Tolerance/multiplier extras: gold = ×10⁻¹, ±5%; silver = ×10⁻², ±10%. Example: brown–black–red–gold = 10 · 10² Ω ± 5% = 1000 Ω = 1 kΩ ± 5%. Reading order: the band closest to a lead is the first; the tolerance band (usually gold or silver) is normally spaced apart from the value bands so you know which side to start.

Applications: DIY electronics and LED sizing

Used in DIY electronics (Arduino, Raspberry Pi, ESP32), board repair and reverse engineering when no datasheet is available. A common task is sizing a current-limiting resistor for an LED: R = (Vsupply − VLED) / ILED. The color code lets you pick the closest standard E12/E24 value from your parts bin without a multimeter — handy when prototyping or working with through-hole components.

FAQ

How do I know which side to read from? The tolerance band (gold or silver) is usually thicker or spaced farther from the others — start from the opposite end. If both ends look symmetric, measure with a multimeter to confirm.

4-band or 5-band? Most general-purpose resistors are 4-band with ±5% or ±10% tolerance. Precision resistors (±1%, ±0.5%) use 5 bands with three significant digits.

What does the 6th band mean? The temperature coefficient (ppm/°C), indicating how much the resistance drifts per degree. Common values: brown 100, red 50, blue 10 ppm/°C.

What about SMD resistors? Surface-mount parts use numeric codes printed on top (e.g., "103" = 10·10³ = 10 kΩ), not color bands.