The Electronic Industries Association (EIA), and then statued by IEC publication 60063, specify standard values for resistors, sometimes referred to as the "preferred value" system.

The value system has its origins in the early years of the last century at a time when most resistors were carbon-graphite with relatively poor manufacturing tolerances. The rationale is simple - select values for components based on the tolerances with which they are able to be manufactured. Using 10% tolerance devices as an example, suppose that the first preferred value is 100 ohms. A value of 105 ohm resistor falls within the 10% tolerance range of the 100 ohm resistor, so the next value outside the range is 120. A 120 ohm resistor has a value ranging between 110 and 130 ohms and the next value might be 150 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, ... (see table below). This gives the E12 series which contains 12 elements.

The EIA "E" series specify the preferred values for various tolerances. The number following the "E" specifies the number of logarithmic steps per decade, or the values in the series. The tables below are normalized for the decade between 100 and 1,000. The values in any decade can be derived by merely dividing or multiplying the table entries by powers of 10. The series are as follows:

• E3 50% tolerance (no longer used)
• E6 20% tolerance (now seldom used)
• E12 10% tolerance
• E24 5% tolerance (and usually 2% tolerance)
• E48 2% tolerance (also for inventory cost control in place of E96)
• E96 1% tolerance
• E192 0.5%, 0.25%, 0.1% and higher tolerances.

A formula to approximate a value for a member in a class is:

V(n) = Round(100*exp((n-1)/N*ln(10)))

where V(n) is value for the n-th member in class E-N (i.e. N=192,96,48,24,12,6,3).