How to read 4-band and 5-band resistor codes
A plain guide to the resistor colour code: which bands are digits, how the multiplier works, and how tolerance and orientation are read.
How the bands are laid out
A resistor packs its value into coloured stripes so it can be read without printing tiny numbers on a curved body. On a common 4-band part the stripes are, from left to right, first digit, second digit, multiplier and tolerance. A 5-band part inserts a third digit stripe before the multiplier, so it carries an extra significant figure. Getting the reading order right is the first step, because a resistor read backwards can give a wildly wrong value.
Digits and the multiplier
The digit colours follow a fixed sequence: black is 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8 and white 9. The multiplier band uses the same order as a power of ten, so a red multiplier scales by 100 and an orange one by 1000. Two extra multiplier colours cover small resistors, with gold as 0.1 and silver as 0.01. Brown, Black, Red therefore means 10 times 100, or 1000 ohm.
The tolerance band
The final band states how far the true resistance may stray from the coded value. Gold means plus or minus 5 percent and silver means plus or minus 10 percent, the everyday choices, while brown at 1 percent and red at 2 percent mark tighter precision parts. Blue, green, violet and grey push tolerance below 1 percent for demanding work. This tool reports the tolerance as a plus-or-minus percentage right next to the resistance.
Getting the orientation right
Resistors are not marked with an arrow, so you decide which end comes first. The trick is that the digit bands are usually clustered toward one end while the tolerance band sits a little apart after a wider gap. Keep that lone band on the right and read left to right. If the colours produce an odd value, flip the part and read the other way, then compare against a standard resistance to confirm.