Resistor Color Codes

Resistors are often labeled with four color bands to indicate their resistance. The bands are read in order, starting at the end of the resistor with a color band nearest it. The first two bands are read as a two digit number. The third band is read as a power of 10 multiplier of that number.

resistance value in ohms = (a two digit number from the first 2 bands) × 10^{(third band digit)}

The fourth band is an indicator of the tolerance of the resistor. The tolerance is stated as a percent of the labeled value, which is the most that the actual resistance can differ from the labeled value.

For example a resistor with the color bands  red/orange/green/gold  would be   23×10⁵W ± 5%