What Are the Standard Resistor Values?

It's essential to use the correct value resistors for your electronics projects. Find out all about standard resistor values.

Choosing the correct resistor for any given application requires a little bit of background knowledge. Understanding the ohmage of your resistor is crucial, but you should also have a grasp of standard resistor values. But what are the most common resistor values and what do they mean?

First defined in 1952 by the IEC (International Electrotechnical Commission), resistor values aim to standardize the resistance and tolerance of resistors across the world. This makes it easier for consumers and electrical engineers to pick the right components for their circuits. It also provides manufacturers with a template to follow.

Using resistors of the wrong values can lead to unexpected results within a circuit. For example, if you use a resistor with poor tolerances with a sensitive LED, you run the risk of too much power making it to the LED. This can cause circuits to fail and even damage components. A standard surface-mount resistor's ohmage and tolerance can be found by reading resistor color codes.

Preferred values, also known as E-series, are split into groups based on their tolerance. The tolerance of a resistor describes the potential difference between its rated resistance and its actual resistance.

For example, an E3 series resistor has a tolerance of 40%. This means that an E3 resistor with a resistance rating of 100 ohms will actually have a resistance between 60 and 140 ohms. Each series is split further into a set of resistance values.

Each E series has its own set of resistance values that sit between one and ten, with the number of steps (on a logarithmic scale) being equal to the E number. These values represent the different ohmage options available within the series, and they can be multiplied by 10, 100, 1000, etc. for the full resistance range.

For example, E3 resistors have the following three values; 1.0, 2.2, and 4.7. This means that E3 resistors can have a resistance of 1Ω, 2.2Ω, or 4.7Ω, but they can also have resistances of 10Ω, 22Ω, and 47Ω, or 100Ω, 220Ω, and 470Ω. This continues into millions of ohms.

E6 series resistors have a tolerance of 20% and the following six values.

E12 series resistors have a tolerance of 10% and the following 12 values.

E24 series resistors have a tolerance of 5% and the following 24 values.

E48 series resistors have a tolerance of 2% and the following 48 values.

E96 series resistors have a tolerance of 1% and the following 96 values.

E192 series resistors have a tolerance of 0.5% or lower and the following 192 values.

The value you choose for your resistor should be based on a couple of factors. Price is important, with higher E series resistors generally having a higher cost due to their lower tolerance (i.e. higher accuracy of ohmage value). Alongside this, you also need to consider the requirements of your circuit.

Samuel is a UK-based technology writer with a passion for all things DIY. Having started businesses in the fields of web development and 3D printing, along with working as a writer for many years, Samuel offers a unique insight into the world of technology. Focusing mainly on DIY tech projects, he loves nothing more than sharing fun and exciting ideas that you can try at home. Outside of work, Samuel can usually be found cycling, playing PC video games, or desperately attempting to communicate with his pet crab.