Voltage Divider Calculator
Find output voltage and current of a divider.
Top resistor, between Vin and the output node.
Bottom resistor, between the output node and ground.
Results update as you type.
How it works
A voltage divider uses two resistors in series to produce a smaller, predictable output voltage from a larger input, and this voltage divider calculator returns that output along with the current flowing through the pair. Tap the connection between the two resistors and you get a fraction of the supply voltage set purely by the ratio of the resistor values, which makes dividers one of the most common building blocks in electronics. This matters because dividers appear everywhere: setting reference voltages, scaling a signal down so a microcontroller can safely read it, biasing transistors, and reading sensors like thermistors and light-dependent resistors. Picking the wrong resistor values wastes power or loads the circuit too heavily, so a voltage divider calculator lets you check both the output voltage and the current draw before soldering anything. The formula works because both resistors carry the same series current, so the supply voltage splits between them in proportion to their resistances. The output across the lower resistor is simply the input scaled by that resistor's share of the total. Hobbyists, electronics students, and hardware engineers rely on a voltage divider calculator to design reference levels and sensor front-ends with confidence rather than guesswork.
Vout = Vin × R2 ÷ (R1 + R2)
In a two-resistor divider the same current flows through both resistors, so the input voltage splits across them in proportion to their resistances. The output taken across R2 is therefore Vin scaled by R2 divided by the total resistance R1 plus R2. The series current equals Vin divided by that total resistance, following Ohm's law for the single loop the two resistors form.
Source:Standard electrical engineering
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter input voltage, resistor r1 and resistor r2.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Output voltage updates instantly as you type — no button to press.
Frequently asked questions
How does a voltage divider work?
Two resistors are placed in series across the input voltage, and the output is taken from the point between them. Because the same current flows through both, the input voltage splits across them in proportion to their resistances. The output equals the input multiplied by the lower resistor divided by the sum of both resistors, giving a stable fraction of the supply set entirely by the resistor ratio.
Does connecting a load change the output voltage?
Yes. Attaching a load across the output places its resistance in parallel with R2, which lowers the effective bottom resistance and pulls the output voltage down. To keep the divider accurate, the load resistance should be much larger than R2, or you should account for it in the calculation. This loading effect is the main limitation of a simple resistive divider used as a voltage reference.
How much current does a voltage divider draw?
The series current equals the input voltage divided by the sum of the two resistors. Larger resistor values reduce this current and save power, which matters in battery-powered devices, but they also make the divider more sensitive to loading and noise. Smaller resistors give a stiffer, more accurate output at the cost of higher continuous current. Balancing these two concerns is the core design trade-off.
What are common uses for a voltage divider?
Voltage dividers set reference voltages, scale high signals down to safe levels for analog-to-digital converters, bias transistor stages, and form half of sensor circuits with thermistors, photoresistors, or potentiometers. They are simple, cheap, and require only two components. For any job needing a fixed fraction of a supply voltage with little current, a resistive divider is usually the first tool an engineer reaches for.
Can a voltage divider supply power to a circuit?
Not effectively. A resistive divider is meant to set a reference voltage, not to deliver meaningful current. As soon as a real load draws current, the output sags and the divider wastes power as heat in the resistors. To power a circuit at a lower voltage, use a regulator or a buck converter instead, which hold the output steady under load far more efficiently.