Voltage Divider Calculator
Calculate voltage divider step by step: Vout = Vin × R2 ÷ (R1 + R2).
In short
Formula: Vout = Vin × R2 ÷ (R1 + R2). With a load RL, R2 is replaced by R2 ∥ RL = R2·RL ÷ (R2 + RL).
Output voltage
3.8367 V
- Effective R2
- 4,700 Ω
- Divider current
- 0.8163 mA
- Power in R1
- 6.6639 mW
What this calculator does
Calculate voltage divider step by step: Vout = Vin × R2 ÷ (R1 + R2). Worked example, questions and limitations included.
Use it to turn Input voltage, R1 (top resistor), R2 (bottom resistor), Load resistance on output (optional) into a checked result you can compare, copy, or rerun with different assumptions.
The page shows the formula, a numeric worked example, and the assumptions that affect this electrical calculation.
Inputs and what they mean
- Input voltage
- — number value.
- R1 (top resistor)
- — number value.
- R2 (bottom resistor)
- — number value.
- Load resistance on output (optional)
- — number value.
How to use it
- Enter each value in the unit shown next to the box (use the unit converter first if your numbers are in other units).
- Check the breakdown to see every intermediate step.
- Read the limitations before relying on the result.
Formula
The unloaded formula assumes nothing draws current from the output.
Adding a load lowers Vout; the calculator shows this when you enter a load.
R1 + R2 must be above zero.
Vout = Vin × R2 ÷ (R1 + R2). With a load RL, R2 is replaced by R2 ∥ RL = R2·RL ÷ (R2 + RL).
Inputs used: Input voltage, R1 (top resistor), R2 (bottom resistor), Load resistance on output (optional).
Worked example
12 V into 10 kΩ and 4.7 kΩ
- Vout = 12 × 4,700 ÷ 14,700.
- Vout = 3.837 V.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
- Ignores resistor tolerance (±1% or ±5% shifts the output).
- DC or resistive only.
- Does not model source resistance.
- Results are estimates for planning and learning. Real designs, installations and bids must be checked by a qualified, licensed professional against the codes that apply where you work.
- The result depends on the values you enter for this voltage divider calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.
Common questions
Can I power a device from a voltage divider?
Usually not. Any load current changes the output voltage and wastes power in the resistors. Use a regulator for supplies; dividers suit sensing and reference inputs.
How do I pick resistor sizes?
Use values low enough that the load draws much less current than the divider (a common rule is ten times less), but high enough to keep wasted current small. Check the formula, example, and limitations on this page before using the result for a real electrical decision.
Why does the load field matter?
A meter, ADC input or device in parallel with R2 lowers the effective bottom resistance. Entering it shows the real output voltage.
How do I use the Voltage Divider Calculator?
Enter the required values for Input voltage, R1 (top resistor), R2 (bottom resistor), Load resistance on output (optional). The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.
What formula does the Voltage Divider Calculator use?
Vout = Vin × R2 ÷ (R1 + R2). With a load RL, R2 is replaced by R2 ∥ RL = R2·RL ÷ (R2 + RL). The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.
Can the Voltage Divider Calculator be used for exact decisions?
Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.
Related tools
Calculate electrical power step by step: P = V × I = I² × R = V² ÷ R (DC or resistive AC using RMS values).
Calculate resistance step by step: R = V ÷ I, or for a conductor R = ρ × L ÷ A (A in m²).
Calculate series resistance step by step: R_total = R1 + R2 + … + Rn.