Which resistor is R1 and which is R2?

R1 is the resistor between the input voltage and the output node. R2 is the resistor between the output node and ground, and the output voltage is specifically the voltage measured across R2 — getting these two swapped is the most common source of a wrong divider calculation.

Does this account for a load connected to the output?

No — this calculates the ideal, unloaded output voltage, which assumes whatever you connect to the output draws negligible current compared to what flows through R1 and R2. Connecting a low-resistance load pulls the actual output voltage down below this ideal value, since the load effectively becomes a third resistor in parallel with R2.

Why use a voltage divider instead of a voltage regulator?

A divider is simpler and needs no active components, which is fine for low-current signal scaling (like reading a sensor into a microcontroller's ADC). But because its output sags under load and wastes power as heat through the resistors, a real regulated voltage supply is the better choice whenever the output needs to actually source meaningful current.

How do I choose resistor values, not just the ratio?

The R1:R2 ratio sets the output voltage, but the absolute resistor values matter too: too low wastes power and draws excess current from the source, too high makes the divider more sensitive to any load you connect. A common starting point is choosing values in the kilo-ohm range so the divider draws only a small, predictable current.

Can I use a voltage divider to power something directly?

Not reliably — a divider's output voltage depends on the load drawn from it, so it's suited to signal-level applications like sensor readings or reference voltages, not to actually powering a component that needs a stable, load-independent voltage.

Physics, Chemistry & Engineering Cluster

Voltage Divider Calculator

Calculate output voltage of a resistor voltage divider.

TL;DR: Voltage Divider Calculator is a free, browser-based tool that lets you calculate output voltage of a resistor voltage divider.

Input voltage, Vin (V)

R1 (Ω)

R2 (Ω)

Understanding the Voltage Divider Calculator

The Voltage Divider Calculator computes mechanical, electrical, thermodynamic, and chemical engineering properties using standard physical laws and SI unit conversions.

How It Works

Select your input physical variables and choose your engineering measurement units.
Enter numerical values for the known physical constants and parameters.
View the calculated physical property, force, or energy output.
Review the underlying physical equations and unit derivation breakdown.

Mathematical Formula & Methodology

Here is the standard mathematical equation used to calculate this result accurately:

V_{\text{out}} = V_{\text{in}} \times \frac{R_2}{R_1 + R_2}

Formula Variables Explained:
Computes output voltage across $R_2$ in a passive two-resistor voltage divider circuit.

Step-by-Step Worked Example

For $V_{\text{in}} = 9\text{V}$ , $R_1 = 10\text{k}\Omega$ , and $R_2 = 5\text{k}\Omega$ : $V_{\text{out}} = 9 \times \frac{5}{10 + 5} = 9 \times \frac{1}{3} = 3.0\text{ Volts}$

How to Get the Best Results

Dimensional Consistency: Ensure all input variables are converted to compatible base SI units (Meters, Kilograms, Seconds, Kelvin).
Engineering Safety Factors: In real-world physical structures, always incorporate safety margins (1.5x–3.0x) beyond theoretical yield limits.
Ideal Assumptions: Physical equations model ideal conditions; real-world friction, air resistance, and thermal loss may apply.

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100% Client-Side Privacy Guarantee

All processing runs locally inside your browser using JavaScript and HTML5 APIs. Your data, files, and inputs are never uploaded to any remote server. Complete privacy by design.

Frequently Asked Questions

: R1 is the resistor between the input voltage and the output node. R2 is the resistor between the output node and ground, and the output voltage is specifically the voltage measured across R2 — getting these two swapped is the most common source of a wrong divider calculation.
: No — this calculates the ideal, unloaded output voltage, which assumes whatever you connect to the output draws negligible current compared to what flows through R1 and R2. Connecting a low-resistance load pulls the actual output voltage down below this ideal value, since the load effectively becomes a third resistor in parallel with R2.
: A divider is simpler and needs no active components, which is fine for low-current signal scaling (like reading a sensor into a microcontroller's ADC). But because its output sags under load and wastes power as heat through the resistors, a real regulated voltage supply is the better choice whenever the output needs to actually source meaningful current.
: The R1:R2 ratio sets the output voltage, but the absolute resistor values matter too: too low wastes power and draws excess current from the source, too high makes the divider more sensitive to any load you connect. A common starting point is choosing values in the kilo-ohm range so the divider draws only a small, predictable current.
: Not reliably — a divider's output voltage depends on the load drawn from it, so it's suited to signal-level applications like sensor readings or reference voltages, not to actually powering a component that needs a stable, load-independent voltage.

Cite This Tool

Referencing this tool in a paper, article, or bibliography? Copy a ready-made citation below.

NexLove.org. (2026). Voltage Divider Calculator [Software]. https://nexlove.org/tools/voltage-divider-calculator.html

“Voltage Divider Calculator.” NexLove.org, 2026, nexlove.org/tools/voltage-divider-calculator.html.

NexLove.org (2026) Voltage Divider Calculator. Available at: https://nexlove.org/tools/voltage-divider-calculator.html (Accessed: 2026).

@misc{nexlove_voltage_divider_calculator,
  title = {Voltage Divider Calculator},
  author = {{NexLove.org}},
  year = {2026},
  url = {https://nexlove.org/tools/voltage-divider-calculator.html}
}

Embed This Tool

Add the live Voltage Divider Calculator tool to your own website with this snippet — it loads the real, working tool in an iframe, not a static screenshot.

<iframe src="https://nexlove.org/embed/voltage-divider-calculator.html" width="100%" height="600" style="border:1px solid #e2e8f0;border-radius:12px" title="Voltage Divider Calculator — NexLove.org" loading="lazy"></iframe>

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