Colour Code (idea)

Colour Code (idea)

Tiny resistors are difficult to label with long numbers, so coloured bands can show their resistance.

Colour Code (idea)

Resistors may use coloured bands to indicate their resistance value.

This is called the resistor colour code.

For a common four-band resistor:

Band 1 → first significant digit.

Band 2 → second significant digit.

Band 3 → multiplier.

Band 4 → tolerance.

Digit Colours

Black → 0 Brown → 1 Red → 2 Orange → 3 Yellow → 4 Green → 5 Blue → 6 Violet → 7 Grey → 8 White → 9

Example

Suppose the bands are:

Red — Violet — Brown — Gold

Red = 2.

Violet = 7.

Brown multiplier = ×10.

So:

**27 × 10 = 270 Ω**

Gold commonly represents:

±5% tolerance

Therefore:

270 Ω ±5%

Tolerance

Tolerance tells us the permitted variation around the marked resistance.

A real resistor does not have to be exactly equal to its nominal value.

Colour Code (idea) — Advanced

Colour coding provides compact logarithmic multiplier notation plus manufacturing tolerance, allowing a broad resistance range to be encoded on small components.