Voltage Divider Calculator
Output voltage, current and power for a two-resistor divider.
Enter your values
Enter the input voltage in V.
Enter the r1 (top) in Ω.
Enter the r2 (bottom) in Ω.
Enter the load resistance (optional) in Ω.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Output voltage
- 3.8367 V
- Current through the divider
- 0.8163 mA
- Power in R1
- 6.664 mW
- Power in R2
- 3.132 mW
- Total power
- 9.796 mW
- Divider output impedance
- 3197.3 Ω
Quick answer
A resistive divider outputs Vin × R2 ÷ (R1 + R2), so the voltage splits in proportion to the resistances.
Vout = Vin × R2 ÷ (R1 + R2)
At a glance
| What it does | Output voltage, current and power for a two-resistor divider. |
|---|---|
| Category | Engineering |
| Inputs needed | Input voltage, R1 (top), R2 (bottom), Load resistance (optional) |
| Formula | Vout = Vin × R2 ÷ (R1 + R2) |
| Cost | Free — no sign-up, no download |
How to use the Voltage Divider Calculator
- 1Enter the supply voltage.
- 2Enter both resistor values in ohms.
- 3Add a load resistance to see how much the output sags under real use.
Inputs explained
- Input voltage(V)
- Enter the input voltage in V.
- R1 (top)(Ω)
- Enter the r1 (top) in Ω.
- R2 (bottom)(Ω)
- Enter the r2 (bottom) in Ω.
- Load resistance (optional)(Ω)
- Enter the load resistance (optional) in Ω.
Frequently asked questions
Why does my divider sag under load?
The load sits in parallel with R2, lowering the effective bottom resistance. Keep the load at least 10× R2, or buffer it with an op-amp.
How do I pick resistor values?
Lower values waste more current but resist loading better. For sensing, tens of kilohms is a common compromise.
What do I need to enter into the Voltage Divider Calculator?
Just 4 values: input voltage, r1 (top), r2 (bottom), load resistance (optional). Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Voltage Divider Calculator work out the answer?
A resistive divider outputs Vin × R2 ÷ (R1 + R2), so the voltage splits in proportion to the resistances. It applies the formula Vout = Vin × R2 ÷ (R1 + R2) and shows the working so you can check each step by hand.
Is the Voltage Divider Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.