How to read a 4-band resistor color code
A resistor's color bands encode its resistance value directly on the component, since the actual number is too small to print legibly. On the most common 4-band resistor, the first two bands are significant digits, the third band is a power-of-ten multiplier, and the fourth band states the manufacturing tolerance. Choose a color for each band above and click Calculate to decode the resistance, its tolerance, and the minimum and maximum values the part is guaranteed to fall within.
The standard color code
Each color from black through white stands for a digit 0-9 in the two digit bands, and doubles as a power of ten in the multiplier band: black=0, brown=1, red=2, orange=3, yellow=4, green=5, blue=6, violet=7, gray=8, white=9. Two extra colors appear only on the multiplier band, for resistors below 10 ohms: gold means x0.1 and silver means x0.01. The tolerance band uses its own small set of colors: brown=+/-1%, red=+/-2%, gold=+/-5%, silver=+/-10%, and no fourth band at all traditionally means +/-20%.
The formula
Resistance = (10 x first digit + second digit) x multiplier. For example, brown-black-red-gold reads as 1, 0, x100, +/-5%, giving (10x1+0)x100 = 1,000 ohms, or 1 kilo-ohm, guaranteed to measure within +/-5% of that value — between 950 and 1,050 ohms.
Interpreting the results
The Resistance card shows the nominal value the manufacturer targeted. Tolerance shows how far a real part is allowed to drift from that nominal value. Minimum and Maximum give the guaranteed range — any resistor with this color code should read somewhere between those two figures on a multimeter, even though the value implied by the bands is a single nominal number.