Resistor color code

Resistor stripes follow the same idea as IEC 60062: each color is a digit (0–9), a power-of-10 multiplier, or (on 4- and 5-band parts) a tolerance percentage.

In ohms, the pattern is:

• 4 bands (most common): (10×D₁ + D₂) × 10M and the last band is ±tolerance (e.g. gold ≈ 5%, brown ≈ 1%). The multiplier color sets M from 0 (×1) to 9 (×10⁹), with gold and silver for ×0.1 and ×0.01.
• 5 bands: an extra value digit: (100×D₁ + 10×D₂ + D₃) × 10M, then tolerance.
• 3 bands: the same as 4, but with no tolerance printed on the body. This app assumes about ±20% for the range, which is a typical rule of thumb for unmarked 3-band parts, not a formal fourth stripe.

When you type a value, the tool picks digit and multiplier colors that match (or, if the number cannot be built exactly, the closest combination allowed by that many bands). Tolerance reuses your selected band when you already have 4- or 5-band mode, or defaults to 5% (gold) when you did not.