This LM317, LM338 calculator software is used as a tool to determine the value of the
voltage adjusting resistor needed to assign the output of an LM317 to an
allocated degree. Normally R1 is 220 ohms or 240 ohms, however it could very
well be a different value for instance 150 or 470 ohms. Go with a value for R2
and click the "Calculate" button. The LM317 output value is displayed in volts.
Take into account that the input voltage to the LM317 is required to be a
minimum of 1.5v higher than the output voltage. To increase current you can configure an outboard transistor across the input and output pins of the IC
Very good explained thanks