What is the voltage divider formula?

Vout = Vin × R2 / (R1 + R2). The output is taken across R2, between R2 and ground.

How is the divider current calculated?

By Ohm's law on the series pair: I = Vin / (R1 + R2). The same current flows through both resistors because they are in series.

How much power does the divider dissipate?

Total power is P = Vin × I = Vin² / (R1 + R2). Larger resistor values waste less power but make the output more sensitive to loading.

Does a load affect the output?

Yes. This assumes an ideal, unloaded output. Any load connected in parallel with R2 lowers Vout, so size the resistors so the divider current is much larger than the load current.

How do I pick R1 and R2 for a target output?

Rearrange the formula: R1 / R2 = (Vin − Vout) / Vout. Equal resistors halve the voltage; for a 5 V output from 12 V you need R1 ≈ 1.4 × R2.

Why should a voltage divider not power a circuit directly?

A divider is a reference, not a supply. Drawing meaningful current loads R2 and collapses Vout. Use a regulator or buffer (op-amp follower) when a stable output under load is needed.

Is anything uploaded?

No — all calculations happen locally in your browser.

Voltage Divider Calculator

A resistive voltage divider is one of the most common building blocks in electronics: two resistors in series turn a higher input voltage into a lower, predictable output. It is used to scale sensor signals into an ADC range, set bias points, and create reference voltages. This calculator returns the output voltage plus the current and power so you can size the resistors sensibly.

How it works

The supply Vin feeds the top resistor R1; the output is taken at the node between R1 and R2, with R2 going to ground. Because the two resistors carry the same series current, the output is simply the fraction of the total resistance that R2 represents:

Output: Vout = Vin × R2 / (R1 + R2)
Current: I = Vin / (R1 + R2)
Power: P = Vin × I = Vin² / (R1 + R2)

This is the unloaded (ideal) case — connecting a real load across R2 draws extra current and pulls Vout down, so keep the divider current well above the load current.

Example

With Vin = 12 V, R1 = 10 kΩ and R2 = 10 kΩ:

Quantity	Calculation	Result
Vout	12 × 10000 / 20000	6 V
Current	12 / 20000	0.6 mA
Power	12 × 0.0006	7.2 mW

Equal resistors halve the voltage. Change R2 to 5 kΩ and Vout drops to 12 × 5000 / 15000 = 4 V. All calculations are computed in your browser — nothing is uploaded.