As you probably know, the Electronic Industries Association
(EIA) and other authorities have specified standard values for
resistors. It can be referred as the Preferred Value system. The
preferred 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 E series
specify the preferred values for various tolerances. The number
following the E specifies the number of logarithmic steps per
decade. This is not really a calculator, but a very handy tool
if, like me, you can't remember what values of resistor are
available "from stock". Enter the value of resistor you would
like in the box and the available values from the different
series and the difference (as a percentage) from the required
value is displayed below. This is a rolling calculation and does
not require clearing, just alter the value in the box.