Resistors and capacitors are the most basic building blocks of electronic circuits. They come in different sizes and packages, and each one has a specific resistance or capacitance value. These values are often recommended by data sheets and reference designs—but are also sometimes calculated based on circuit requirements.
Calculated R/C values have infinite precision. Of course, it isn’t feasible to manufacture an infinite number of different resistors and capacitors to cover all such values. Instead, manufacturers guarantee a specific tolerance, like ±5%, and produce a set of components corresponding to that tolerance.
Two of the most commonly used sets of such values are represented in the table here. The 5% set (also known as the E24 series) has 24 values between 100 and 1000, while the 1% set (also known as the E96 series) has 96 values in the same range.
Let’s say we need a 230 kΩ resistor based on some calculations. Checking the table we see that the closest 5% value is 220 kΩ, which is 4.3% below our desired value. The closest 1% value is 232 kΩ, which is 0.9% above our desired value.
In case you want to use the standard E-series values in Python scripts, here are the E12, E24, E48, and E96 series as Python arrays. All values are normalized to the 1.0–10.0 range.
E12 = [
1.0, 1.2, 1.5, 1.8, 2.2, 2.7,
3.3, 3.9, 4.7, 5.6, 6.8, 8.2
]
E24 = [
1.0, 1.1, 1.2, 1.3, 1.5, 1.6,
1.8, 2.0, 2.2, 2.4, 2.7, 3.0,
3.3, 3.6, 3.9, 4.3, 4.7, 5.1,
5.6, 6.2, 6.8, 7.5, 8.2, 9.1
]
E48 = [
1.00, 1.05, 1.10, 1.15, 1.21, 1.27,
1.33, 1.40, 1.47, 1.54, 1.62, 1.69,
1.78, 1.87, 1.96, 2.05, 2.15, 2.26,
2.37, 2.49, 2.61, 2.74, 2.87, 3.01,
3.16, 3.32, 3.48, 3.65, 3.83, 4.02,
4.22, 4.42, 4.64, 4.87, 5.11, 5.36,
5.62, 5.90, 6.19, 6.49, 6.81, 7.15,
7.50, 7.87, 8.25, 8.66, 9.09, 9.53
]
E96 = [
1.00, 1.02, 1.05, 1.07, 1.10, 1.13,
1.15, 1.18, 1.21, 1.24, 1.27, 1.30,
1.33, 1.37, 1.40, 1.43, 1.47, 1.50,
1.54, 1.58, 1.62, 1.65, 1.69, 1.74,
1.78, 1.82, 1.87, 1.91, 1.96, 2.00,
2.05, 2.10, 2.16, 2.21, 2.26, 2.32,
2.37, 2.43, 2.49, 2.55, 2.61, 2.67,
2.74, 2.80, 2.87, 2.94, 3.01, 3.09,
3.16, 3.24, 3.32, 3.40, 3.48, 3.57,
3.65, 3.74, 3.83, 3.92, 4.02, 4.12,
4.22, 4.32, 4.42, 4.53, 4.64, 4.75,
4.87, 4.99, 5.11, 5.23, 5.36, 5.49,
5.62, 5.76, 5.90, 6.04, 6.19, 6.34,
6.49, 6.65, 6.81, 6.98, 7.15, 7.32,
7.50, 7.68, 7.87, 8.06, 8.25, 8.45,
8.66, 8.87, 9.09, 9.31, 9.53, 9.76
]