4-Band Resistor Color Code

You pull a loose resistor out of the drawer and the bands read brown, black, red, gold. Instead of hunting for a colour chart and counting zeros, pick the four colours in the dropdowns and the value shows up in ohms with the tolerance beside it: 1000 Ω ±5% in that example. The first two selects are the digits, the third is the multiplier and the fourth is the tolerance.

The part most pages skip is reading direction. The tolerance band, gold or silver, always sits at the far end and usually has a wider gap before it. Read the body backwards and brown-black-red turns into red-black-brown, landing you an order of magnitude away. The multiplier can also be gold (x0.1) or silver (x0.01), which is how 1 Ω and 4.7 Ω parts exist with only four bands.

The output is plain ohms with no prefix, so 4700 Ω is the 4k7 from the datasheet. Tolerance tells you how far the real part may sit from that figure: a legitimate 4700 Ω ±5% measures anywhere from 4465 to 4935 Ω on the meter and is still in spec. If your resistor has five bands, meaning three digits before the multiplier, use the 5-band version instead. The maths runs in your browser.