Voltage Divider Calculator (Output Voltage $V_{out}$ & Resistor Values)
Calculate output voltage, resistor ratios, and loaded voltage divider circuits.
TL;DR: Voltage Divider Calculator computes the output voltage of a resistive divider circuit using the formula $V_{out} = V_{in} \times [R_2 / (R_1 + R_2)]$.
What Is a Voltage Divider and What Is the Voltage Divider Formula?
A voltage divider is a fundamental linear electrical circuit that produces an output voltage (Vout) that is a fraction of its input voltage (Vin). The unloaded voltage divider formula is: Vout = Vin × [R2 / (R1 + R2)], where R1 is the top resistor and R2 is the bottom resistor connected to ground.
How to Use the Voltage Divider Calculator
Our Voltage Divider Calculator performs high-precision mathematical operations directly in your browser with zero latency and complete client-side privacy.
- Enter the Input Voltage ($V_{in}$) in Volts.
- Enter Resistor 1 ($R_1$) and Resistor 2 ($R_2$) values in Ohms ($\Omega$), k$\Omega$, or M$\Omega$.
- Optionally enter a Load Resistance ($R_L$) connected in parallel with $R_2$.
- Click 'Calculate Voltage Divider' to compute output voltage ($V_{out}$) and circuit current.
- Review power dissipation across both resistors ($P = I^2 R$) to verify component wattage ratings.
Mathematical Formula & Equations
Computes output voltage across $R_2$ in a passive two-resistor voltage divider circuit.
Calculation Example
For $V_{\text{in}} = 9\text{V}$, $R_1 = 10\text{k}\Omega$, and $R_2 = 5\text{k}\Omega$: $$V_{\text{out}} = 9 \times \frac{5}{10 + 5} = 9 \times \frac{1}{3} = 3.0\text{ Volts}$$
100% Client-Side Privacy & Data Security
All calculations, amortization schedules, variables, and sensitive numerical datasets execute 100% locally in your web browser memory. Your financial, medical, and personal values are never transmitted, logged, or uploaded to any external server.
Frequently Asked Questions
- The standard formula is `Vout = Vin × (R2 / (R1 + R2))`.
- A load resistor connects in parallel with R2, creating an equivalent resistance `R2_eff = (R2 × RL) / (R2 + RL)`. This lowers the effective output voltage compared to the unloaded circuit.
- Choose resistor values that draw about 10 times more current than the expected load current to prevent loading voltage drops, while keeping resistance high enough to avoid wasting battery power.
- No. Voltage dividers are inefficient for powering heavy loads because excess voltage is dissipated as heat. Use linear regulators or switching buck converters for power supply applications.
- Power is calculated as: `P1 = (Vin - Vout)² / R1` and `P2 = Vout² / R2`. Ensure resistor power ratings (e.g., 1/4W, 1/2W) exceed these values.
- The output voltage is: `V_out = V_in × [R2 / (R1 + R2)]`.
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