 How do I know what level resistance my resistor has?

Through hole resistors like the ones in your projects have a series of bands on them that indicate how much resistance they provide. A resistor chart like the one below helps to decode the bands: For example, let’s take a 4-band resistor that has red, red, brown and gold bands. Each red band corresponds to a value of 2, so we start with 22. The third band is the multiplier. In this case, brown means multiply by 10. Se we have 22 x 10, or 220 ohms.

The gold band is the tolerance. Gold means 5% tolerance. Since 5% of 220 is 11, we know the actual resistance of this resistor is between 209 and 231 ohms.

Now let’s try a 5 band resistor with brown, black, black, brown, and gold bands. Here brown is 1 and black is 0, so we have 100. The fourth band is our multiplier, and brown means multiply by 10. So we have 100 x 10, or 1000 Ohms. This is typically written as 1K ohms, where K = 1000. Again we have 5% tolerance, so the actual resistance is between 950 and 1050 ohms.

We’ll discuss in a future post how to determine the level of resistance that is needed for a component in a circuit, but for now you can just follow your project instructions to find the right one.