Voltage Divider
Solve resistor divider voltage, input, and resistor values
About this calculator
The Voltage Divider Calculator solves the two-resistor divider equation Vout = Vin·R2/(R1 + R2) for any of the four values — output voltage, input voltage, or either resistor — and reports the divider ratio as a percentage. All values must be positive, and requests where Vout would meet or exceed Vin are rejected as impossible, since a passive divider can only step a voltage down.
How to use the Voltage Divider calculator
- Enter the quantities you know, using the units shown on each field.
- Read the computed results — they update instantly as you type.
- Use the visual explanation to see how the quantities relate.
- Copy the page URL to share the exact calculation.
Common examples
- Vin 12 V, R1 10 kΩ, R2 20 kΩ → Vout 8 V (ratio 66.67%)
- Vin 9 V, R1 1 kΩ, R2 2 kΩ → Vout 6 V
- Divide 5 V down to 3.3 V with R1 = 10 kΩ → R2 ≈ 19411.76 Ω
- R1 4.7 kΩ, R2 10 kΩ, Vout 5 V → Vin 7.35 V
Frequently asked questions
How does the Voltage Divider calculator work?
Enter the known quantities and the calculator applies the governing physical law or scientific formula to find the unknowns, stating the equation it used and the units of every result. Computations run at high precision.
When would I use the Voltage Divider calculator?
It suits physics and chemistry homework, lab work, engineering estimates, and any time you want to explore how changing one quantity affects the others in a well-defined scientific relationship.
How accurate are the results?
The formula itself is evaluated at 30 significant digits of precision. Keep in mind that idealized models — such as neglecting friction, air resistance or measurement error — bound the real-world accuracy more than the arithmetic does.
Can I share a specific calculation with someone else?
Yes. Every value you enter updates the URL, so copying the address bar and sharing the link reopens the exact same calculation for whoever clicks it.