Voltage Divider Calculator

A voltage divider is a simple passive circuit made of two resistors in series that produces an output voltage (Vout) which is a fraction of the input voltage (Vin). The output is taken from the junction between the two resistors, and its value depends on the ratio of R2 to the total resistance (R1 + R2).

The output voltage is calculated using Vout = Vin × R2 / (R1 + R2). Here, Vin is the source voltage, R1 is the upper resistor, and R2 is the lower resistor connected to ground. This formula is derived directly from Ohm's Law.

Yes. This calculator lets you select the unit for each resistor independently — ohms (Ω), kilohms (kΩ), or megaohms (MΩ). Just enter your numeric value and choose the matching unit from the dropdown.

When R1 equals R2, the output voltage is exactly half the input voltage. For example, with Vin = 12 V and R1 = R2 = 10 kΩ, the output Vout will be 6 V.

In real circuits, any load connected across R2 adds a parallel resistance, which effectively reduces R2's value and lowers Vout. The calculated result assumes an ideal unloaded condition with no current drawn by the load.

Voltage dividers are used for signal level adjustment, setting bias voltages for transistors and op-amps, reading analog sensors with a microcontroller, and creating reference voltages. They are best suited for low-current, low-power applications.

The current through the resistor chain is I = Vin / (R1 + R2), following Ohm's Law. This calculator displays the result in milliamps (mA) for convenience. Keep in mind this is the quiescent current with no load attached.

Resistor voltage dividers are not suitable for high-current loads because attaching a load changes the effective resistance and shifts Vout. They also dissipate power continuously. For stable regulated output under varying loads, a dedicated voltage regulator is recommended instead.