Selecting Resistor ratio, the calculator finds the resistors that will most closely match the desired ratio.

Selecting Voltage divider, the calculator first converts the voltage ratio into the equivalent resistor ratio, and then searches for it. Suppose we want the voltage divider ratio D = R1/(R1+R2), the calculator converts it to the resistor ratio R1/R2 = D/(1-D), and searches for that ratio.

After searching for the ratio, try the inverse of the ratio. Sometimes this has a better result for the Series and Parallel cases, and it just means that we swap the resistances of the numerator and denominator.

The resistors are chosen from the set {1Ω <= R < 1GΩ}. The target resistance values of the numerator and denominator are geometrically centered on this range, or on 31.6KΩ.

Ratios are compared with the desired ratio using geometric distance (rather than algebraic). For example the ratios 11 and 9.090909... are of equal geometric distance (10%) from the desired ratio 10. Even though the effect is subtle, applications using ratios are likely to benefit from this type of comparison.