How the colour code works
A resistor too small to print numbers on is labelled with coloured bands instead. On a four-band part the first two bands are significant digits, the third is a multiplier (a power of ten), and the fourth states the manufacturing tolerance. Each colour maps to a fixed number, so the stripes spell out the value.
The value is read as (first digit × 10 + second digit) × multiplier, in ohms. For example brown-black-red means 1, 0 and ×100, giving 1000 Ω, or 1 kΩ.
Reading the bands in the right order
Direction matters — read the wrong way and the value is nonsense.
- Orient the resistor with the tolerance band (usually gold or silver, and often slightly separated) on the right.
- Read the remaining bands from left to right as digit, digit, multiplier.
- Gold and silver multipliers mean fractional values (×0.1 and ×0.01) for sub-10-ohm resistors.
- If both ends look similar, the band nearest a lead or the wider gap is typically the tolerance.
What tolerance means
The tolerance band tells you how far the real resistance may stray from the marked value. A ±5% gold band on a 1 kΩ resistor allows anything from 950 to 1050 Ω. Tighter tolerances (±1% brown, ±0.5% green) cost more and are used where precision matters; everyday parts are commonly ±5%.
Beyond the four-band code
This calculator decodes the standard four-band scheme. Precision resistors often use five or six bands, adding a third significant digit and sometimes a temperature-coefficient band, which this tool does not cover. When a part has more than four stripes, decode it with a five- or six-band reference instead.
Formula
resistance = (digit1·10 + digit2) × multiplierFrequently asked questions
- How do I read which end to start from?
- Hold the resistor so the tolerance band (usually gold or silver) is on the right, then read the bands left to right.