Historically, the E series is split into two major groupings: E3, E6, E12, E24 are subsets of E24. Values in this group are rounded to 2 significant figures. E48, E96, E192 are subsets of E192. Values in this group are rounded to 3 significant figures.

E12 Series. The E12 series has twelve values or steps per decade and hence provides better precision as compared to both the E3 and E6 series. The values per decade in the E12 series are – 1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, and 8.2. It’s widely used in applications where moderate precision is required.

Complete list of the standardized E12 resistor series.

The 120 ohm resistor has a value ranging between 110 and 130 ohms. Following this logic, the preferred values for 10% tolerance resistors between 100 and 1,000 ohms would be 100, 120, 150, 180, 220, 270, 330 and so on (rounded appropriately); …

To understand the E-series sets of preferred values, we will examine the E12 in detail. E12 means that every decade (0.1-1.0, 1-10, 10-100, etc.) is divided in 12 steps on a logarithmic scale. The size of every step is equal to: $$10^{(\frac{1}{12})} = 1.21$$

e192 e96 e48 e192 e96 e48 e192 e96 e48 e192 e96 e48 e24 e12 e6 e3 100 100 100 178 178 178 316 316 316 562 562 562 10 10 10 10 101 180 320 569 11 102 102 182 182 324 324 576 576 12 12 104 184 328 583 13 105 105 105 187 187 187 332 332 332 590 590 590 15 15 15 106 189 336 597 16 107 107 191 191 340 340 604 604 18 18 ...

In industrial design, preferred numbers (also called preferred values or preferred series) are standard guidelines for choosing exact product dimensions within a given set of constraints. Product developers must choose numerous lengths, distances, diameters, volumes, and other characteristic quantities.

E12数系的公比为 系列的电阻规定几个基本系数，这些系数再乘以10An（其中n为整数），即 为某一具体电阻器阻值。 如1.2X101=12Q 误差稍大，较少采用，此系列可用于电阻、电容、电位器、电感等 E24 E代表指数间隔的意思，24表示有24种数字系列

E12 resistors are frequently used as current-limiting resistors in LED circuits. They ensure that the correct amount of current flows through the LED, preventing damage and ensuring proper operation. The E12 series provides suitable values for common LEDs, making them a cost-effective choice for these simple applications.

E12 means that every decade (0.1-1, 1-10, 10-100 etc) is divided in 12 steps. The size of every step is equal to: Formula for preferred values for resistors 10^(1/12)=1.21 One could also say every value is 21% or 1.21 times higher than the last, rounded to whole numbers.