🎨Resistor Colour Code

Reading the bands

Choose 4-band or 5-band, set each band's colour, and the drawing updates with the value — brown-black-red-gold is 10 × 100 = 1 kΩ at ±5%. Four-band parts carry two significant digits and a multiplier; five-band precision parts carry three digits, which is how 1% resistors express values like 4.99 kΩ.

Orientation: the tolerance band — gold or silver, usually set slightly apart — goes on the right. Read the wrong way round, brown-black-red becomes red-black-brown and your 1 kΩ becomes 2 kΩ; if a reading seems absurd for the circuit, flip it.

The code, memorably

The digit colours 0–9 run black, brown, red, orange, yellow, green, blue, violet, grey, white — generations of engineers learned them with a mnemonic; a printable modern one is Big Brown Rabbits Often Yield Great Big Vocal Groans When... pick your own. Gold and silver appear as multipliers (×0.1, ×0.01) and tolerances (±5%, ±10%).

Aging plays tricks: brown darkens toward red, and a hot resistor's bands discolour. A multimeter settles any argument, and desoldering one leg first stops the rest of the circuit skewing the measurement. Once the value is known, Ohm's law turns it into currents and power — and confirms whether the poor resistor was within its wattage in the first place.

Frequently asked questions