Resistor Color Code Band Reader & Calculator

Four color bands, decoded into a resistance value

Brown-black-red-gold decodes to 1 kilo-ohm (1,000 ohms) with a 5% tolerance -- brown (1) and black (0) form the two significant digits '10', red is the multiplier (x100), and gold indicates the tolerance band.

The standard 4-band system encodes: first two bands as significant digits, third band as a power-of-10 multiplier, and fourth band as tolerance -- 10 (from brown-black) x 100 (red multiplier) = 1,000 ohms, which is exactly 1 kilo-ohm in the more commonly spoken unit.

5% tolerance (from the gold fourth band) means the actual resistance of a real physical resistor with these bands could reasonably measure anywhere from 950 to 1,050 ohms and still be considered within spec -- tolerance isn't a defect, it's a manufacturing precision spec the resistor is guaranteed to meet.

Why gold and silver are special cases among the multiplier colors

Standard 4-band IEC colors. Gold and silver multipliers are 0.1 and 0.01. Most multiplier band colors represent positive powers of 10 (black=1, brown=10, red=100, and so on upward), but gold and silver break that pattern specifically as multiplier colors, representing 0.1 and 0.01 respectively -- used for resistors valued below 10 ohms, where a fractional multiplier is needed rather than a whole-number one.

This color-to-number mapping follows a standardized IEC convention used industry-wide, which is what makes color-code resistors reliably readable by anyone trained on the standard, regardless of manufacturer.

A resistor with a 5-band code (adding an extra digit band for higher precision) follows a related but expanded version of this same logic -- three significant digit bands instead of two, then a multiplier and tolerance band, used for tighter-tolerance precision resistors.

Related electronics identification tools

For decoding a capacitor's printed numeric value marking rather than a resistor's color bands, the Capacitor Value Code Converter handles that related but differently-coded component.

Once you have a resistance value, the Ohm's Law Calculator uses it to solve for voltage, current, or power in an actual circuit.

Frequently Asked Questions (FAQ)