Standart Resistor Values
Resistor values are organised into a set of different series of preferred values or standard resistor values.
These standard resistor values have a logarithmically based sequence and this enables the different values to be spaced in such a way that they relate to the component tolerance or accuracy.
Resistor tolerances are generally ±20%, ±10%, ±5%, ±2% and ±1%. More accurate tolerances are available for some resistors, but these are not as widely available and costs are higher.
By having these standard resistor values, electronic components from a variety of manufacturers can be chosen, making sourcing much easier and the cost of the components much less.
Interestingly the same approach and sets of value ranges are used by a number of other electronic components including capacitors, Zener diodes, inductors, etc.