Entering a value for Gain will find the optimum values for R1 and R2. If you specify the values for R1 and R2, the gain is found. If you enter a resistor values (R1 or R2) along with the gain, the other value will be found.

The circuit configuration shown is one flavor of differential amplifier. It take the difference between the inputs (V2 - V1) and provides an amplified version of it at the output. To maximize the common mode rejection, the values pairs (R1 & R3 as well as R2 & R4) should be closely matched. The use of 1% or better tolerance resistors is recommended for best performance.

If you don’t like the magnitude of the resistor values found, you can divide or multiply the values by a multiple of ten and the resultant values will still be a standard value.

This solver uses the following equation to compute its values.