Technical utilities
Voltage Divider Calculator
Divider output equals input voltage multiplied by the lower resistance divided by total series resistance. A connected load appears in parallel with the lower resistor.
Calculate two-resistor divider output, current, and the effect of an optional load resistor.
Calculated result
Divider output
Calculating…
Calculated locally in your browser
Planning math only. Verify equipment specifications and installation requirements separately.
What this calculator returns
A lower load resistance pulls the output below its unloaded value and increases source current.
Formula and variables
The calculation runs entirely in your browser. Static formulas, definitions, examples, and tables remain readable without JavaScript.
Vout = Vin × Rbottom/(R1 + Rbottom), where Rbottom = R2 || Rload when loaded.
- V
- Voltage across the modeled component or network.
- I
- Current through the modeled component or network.
- R
- Resistance in ohms; subscripts identify individual resistors.
- P
- Power dissipated or delivered, in watts.
R1 is the upper resistor; R2 and optional Rload form the lower equivalent resistance.
Worked example
| Input | Value |
|---|---|
| Input voltage | 12 V |
| Upper resistor R1 | 1000 Ω |
| Lower resistor R2 | 1000 Ω |
12 V with R1 = 1 kΩ and R2 = 1 kΩ gives 6 V unloaded.
Reference table
| Solve for | Formula variants |
|---|---|
| Voltage | V = I × R; V = P / I; V = √(P × R) |
| Current | I = V / R; I = P / V; I = √(P / R) |
| Resistance | R = V / I; R = V² / P; R = P / I² |
| Power | P = V × I; P = I² × R; P = V² / R |
| Networks | Series: Req = ΣR; parallel: 1/Req = Σ(1/R) |
Frequently asked questions
Why does adding a load change divider voltage?
The load appears in parallel with the lower resistor, reducing the lower equivalent resistance and usually lowering output voltage.
Can a voltage divider power a large load?
This tool only models ideal steady-state resistors. A low-resistance load can change the output substantially and increase dissipation.
Assumptions and limitations
- Ideal resistors and DC steady state.
- No tolerance, noise, or transient model.
Method and sources
Review the electrical formulas, calculation methodology, and reference tables for the references most relevant to this calculation. The broader technical sources index records source scope and verification. Last reviewed .