Jeff, he of the mightyOhm, asks:
Have you ever wondered why standard 5% resistors have strange values, like 330 and 470 Ohms, instead of nice round numbers like 300 or 500 Ohms?
It turns out that standard resistor values form a preferred number series defined by the EIA. 5% values are part of a standard called E24. The standard is based on a geometric series – each value is approximately 1.1 times the previous one in the set.
4 thoughts on “EIA resistor values explained”
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I remember when I figured this out. I was so proud of myself. And if you look at 1% resistors, it’s the same thing but at a finer resolution.
If you think about it, there’s no reason to have a higher resolution than the accuracy of the resistor.
Like linear dimensions with the “Renard numbers” : R5, R10, R20, and R40 … or the rounded values…