LM317 Adjustment Resistor Calculator

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Introduction:

Use this tool to quickly calculate the resistor value required to set an LM317 adjustable voltage regulator to your desired output voltage.
The LM317 is a popular three-terminal adjustable linear voltage regulator commonly used in power supplies, battery chargers and electronic projects. Its output voltage is set using two external resistors connected to the regulator's adjustment (ADJ) pin. By entering your required output voltage and the value of the known resistor, this calculator determines the appropriate value for the second resistor.
The calculator uses the standard LM317 output-voltage formula and provides the calculated adjustment resistor value in ohms (Ω). You can then select the nearest standard resistor value for your circuit.
Whether you are designing a new LM317 power supply, modifying an existing circuit, or simply checking your resistor calculations, this tool provides a quick way to determine the resistor values needed for the required LM317 output voltage.
Click on any of the links at the top of the page to reveal (or hide) more information about this calculator.

Caveats:

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Definitions:

V: Output Voltage of the circuit.
R1: Value of Resistor between V_out and V_adj pins, typically specified as 220Ω
R2: Value of Resistor between V_adj and circuit ground.

Formulae:

V = 1.25 * (1 + R₂ / R₁)

Instructions

Enter a value into each text-box in the form below.
Choose appropriate unit-sizes for each value from each drop-down list.
Hit the ENTER or RETURN key on your keyboard, or press the 'CalcResult' button below the input fields.
A results area will appear at the bottom of the page, showing the required resistance value.
Press the 'Clear Results' button if you wish to discard the current results list, otherwise further calculations will be added to the bottom of the current results list.