LM 317 Calculator

The LM317T is an extremely common positive voltage regulator - many laboratory supplies and other equipment are based on it. It can produce any amount between 1.25V and up to 35V by adjusting the resistance (opposition to current) between its adjustment pin and ground.

This calculator is used to find the value of the voltage adjustment resistor value required to set the output of an LM317 to a specified level. Typically R1 is 220 ohms or 240 ohms, but it could be some other value. For more information please check out the LM117 / LM317A / LM317 Datasheet.

Note 1: The input voltage to the LM317 must be at least 1.5v greater than the output voltage.

Note 2: You can get ridiculous values with the right combination of R1 and R2. Please note the actual capability of the device from the Data Sheet.

Select a value for R2 and hit the Calculate button. The LM317 output value is reported in volts.

R1 resistor
R2 resistor
Output Voltage