Resistor Color Code Calculator

How the EIA Color Code Works

Resistors use the standardized EIA-RS-279 color code to print their value directly on the component body, since a physical number would be impractical on something a few millimeters long. On a 4-band resistor, the first two bands are significant digits, the third is a power-of-ten multiplier, and the fourth is the tolerance. A 5-band resistor (common on higher-precision parts) adds a third significant digit, pushing the multiplier and tolerance to bands four and five. The digit-to-color mapping follows a fixed sequence: black=0, brown=1, red=2, orange=3, yellow=4, green=5, blue=6, violet=7, gray=8, white=9. This calculator reads the bands you select and computes resistance = (significant digits) × (multiplier), then applies the tolerance to show the guaranteed range of the actual part.

Reading Direction and Tolerance Colors

Always read a resistor from the end farthest from the tolerance band, since tolerance is the giveaway for orientation — it's usually gold or silver and sits alone at one end with a visibly larger gap separating it from the digit bands. Gold and silver only ever appear as a multiplier (×0.1 or ×0.01) or a tolerance (±5% or ±10%), never as a significant digit, which is why they're excluded from the first digit options above. A resistor with no fourth band at all is assumed to carry a ±20% tolerance, though that's rare on modern parts.

Working With the Result

Once you know a resistor's rated value, you can pair it with the Ohm's Law calculator to find the current or voltage drop it produces in a circuit, or use the voltage drop calculator for longer wire runs. Real-world resistors are manufactured in standardized value series (E12, E24, E96) rather than arbitrary numbers, which is why the "nearest standard value" lookup above snaps your target resistance to a value that a manufacturer would actually produce.