ISO 3:1973 is a standard that is part of the International Organization for Standardization and is titled “Preferred numbers— Series of preferred numbers.” A set of recommended numbers that are utilized in many technical and scientific domains is defined by this standard. Preferred numbers provide a collection of values that are uniformly spaced on a logarithmic scale, making calculations and measurements easier.
Several series of preferred numbers, such as the E3, E6, E12, E24, E48, E96, and E192 series, are specified in the ISO 3:1973 standard. The number of values and the ratio between neighbouring values in these series vary.
The E3 series, for example, has three values for each decade (that is, every power of ten), and the ratio between consecutive values is roughly 2.15.