Resistor Divider Calculator

The following calculator works out either \( V_{in} \), \( R_1 \)$, \( R_2 \), or \( V_{out}\), given the other three parameters, using the resistive voltage divider equation:

\( V_{out}=\frac{R_2}{R_1+R_2}V_{in} \)

where:
\( V_{in} \) = input voltage
\( R_1 \) = resistance of resistor 1 (see diagram)
\( R_2 \) = resistance of resistor 2 (see diagram)
\( V_{out} \) = output voltage

It is assumed that the output impedance on \( V_{out} \) is significantly higher than \( R_2 \) so that it doesn't matter (for example, \( V_{out} \) is connected to an op-amp input, analogue microcontroller input or similar).

The quiescent current through the divider, \( I_q \), is also calculated, which can be useful to know when designing power-saving circuits. The equation to find \( I_q \) is:

\( I_q = \frac{V_{in}}{R_1+R_2} \)

Variables: Values: Units: Calculate What? Variable Diagram:
\( V_{in} \)
\( R_1 \)
\( R_2 \)
\( V_{out} \)
\( I_q \)

Featured on the Resistors page.