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Voltage Divider Calculator

Calculate voltage divider output voltage, resistor values, current, power dissipation, loading effects, and resistor networks for accurate analog and digital circuit design.

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V
Please enter all valid positive values.
RESULTS
Vout Ideal
V
Divider Current
A
Power in R1
W
Power in R2
W
Ratio
Rtotal
Ω
Thevenin R
Ω
WITH LOAD
R2 || Rload
Ω
Vout Loaded
V
Loading Ratio
Load Current
A

Diagrams & Theory

Custom SVG diagrams show ideal divider and loaded divider. Load section appears only when the checkbox is enabled.

Without Load Vin R1 R2 Vout Vout = Vin × R2/(R1+R2) With Load Vin R1 R2 Vout RL Loaded: R2 becomes R2 || Rload

Formulas & Mathematical Logic

Vout Ideal = Vin × R2 / (R1 + R2)
Divider Current = Vin / (R1 + R2)
Power in R1 = I² × R1
Power in R2 = I² × R2
Rth = R1 || R2
With load: Rp = R2 × Rload / (R2 + Rload)
Vout Loaded = Vin × Rp / (R1 + Rp)

How to Use This Calculator

Enter Vin, R1 and R2.
Keep load unchecked for ideal divider output.
Tick Enable load resistance to enter Rload.
Click Calculate to show ideal and optional loaded results.

About This Calculator

Voltage divider calculator with optional loading effect.

This tool calculates ideal voltage divider output and optional loaded output when a real circuit is connected to Vout.

A voltage divider uses two resistors to scale an input voltage down. Without load, output depends only on R1 and R2. With a load connected, the load appears in parallel with R2 and usually reduces output voltage. This matters for ADC inputs, sensor dividers, logic-level scaling, battery sensing and microcontroller input circuits.

Ideal OutputUses only R1 and R2.
Loaded OutputUses R2 parallel with Rload.
RthThevenin resistance for RC and ADC settling checks.
PowerChecks resistor dissipation.
Tip: For accurate ADC readings, keep input/load impedance much higher than R2 or use a buffer.

Frequently Asked Questions

What is a voltage divider?

A voltage divider is a two-resistor circuit that creates a lower output voltage from a higher input voltage.

What does load resistance do?

Load resistance connects across the output and acts in parallel with R2, changing the divider ratio.

Why is loaded Vout lower?

Because R2 parallel Rload is smaller than R2 alone, so the output node is pulled down.

What is Thevenin resistance?

It is R1 parallel R2 and helps estimate ADC settling and RC filtering behavior.

Can this be used for ADC scaling?

Yes, but check input impedance, sampling capacitor requirements and divider current.

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About this tool

Voltage Divider Calculator is a free online calculator tool. Use it to get instant, accurate results for your electronics calculations.