Voltage Divider Calculator
Voltage divider calculator: output voltage of a two-resistor divider, or the resistor needed for a target voltage, with current and power.
Vout = Vin · R₂R₁ + R₂
How to use this calculator
- Choose the quantity you want under “Solve for”.
- Type the known values and pick their units: any combination works.
- The result updates as you type. Open “Show the steps” to see the substitution.
Vout = Vin × R2 ÷ (R1 + R2) with no load. A load on the output lowers Vout; keep its resistance at least 10× R2.
Formula
Vout = Vin · R₂R₁ + R₂
| Symbol | Quantity | Units |
|---|---|---|
| Vin | Input voltage | V, mV, µV, kV |
| R₁ | Resistor R₁ (top) | Ω, mΩ, kΩ, MΩ |
| R₂ | Resistor R₂ (bottom) | Ω, mΩ, kΩ, MΩ |
| Vout | Output voltage | V, mV, µV, kV |
Worked example
Given: Vin = 12 V · R₁ = 10 kΩ · R₂ = 4.7 kΩ
Vout = Vin R₂R₁ + R₂
Result: Vout = 3.83673 V
Output voltage for different values of Input voltage
| Vin · Input voltage | Vout · Output voltage |
|---|---|
| 6 V | 1.9184 V |
| 9 V | 2.8776 V |
| 10.8 V | 3.4531 V |
| 12 V | 3.8367 V |
| 13.2 V | 4.2204 V |
| 15 V | 4.7959 V |
| 18 V | 5.7551 V |
| 24 V | 7.6735 V |
Other values as in the worked example.
Frequently asked questions
12 V with R1 = 10 kΩ and R2 = 4.7 kΩ?
Vout ≈ 3.84 V, 0.82 mA through the divider.
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