Voltage Divider Calculator – Vout, Load Effect & Solve for R2
A voltage divider scales a voltage down with two resistors. It is great for feeding an ADC or setting a reference, but the output sags if the load draws significant current compared with the divider current.
V
= 12 VΩ
= 10 kΩSI shorthand works: 10k, 4k7, 1MΩ
= 3.3 kΩΩ
Results
- Vout
- 2.977 V
- Ratio
- 0.2481
- Divider current
- 902.3 µA
- Power in divider
- 10.83 mW
- Output impedance (R1∥R2)
- 2.481 kΩ
Pro
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Vout: 2.977 V
Formula
- Vout = Vin · R2 / (R1 + R2)
- With load: R2' = R2 ∥ RL
FAQ
- Can I power a circuit from a divider?
- Usually not. Its output impedance is R1∥R2, so any real load pulls the voltage down. Use a regulator instead.
- How big should the resistors be?
- For ADC inputs, keep R1∥R2 below what the ADC datasheet recommends (often ≤10 kΩ), or add a capacitor on the output.