Voltage Divider Calculator
Calculate output voltage from a resistor divider.
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V
Ω
Ω
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Frequently Asked Questions
What is the voltage divider formula? +
Vout = Vin x (R2 / (R1 + R2)). This formula assumes negligible current draw from the output. If a load is connected, you need to account for its resistance in parallel with R2.
When should I use a voltage divider vs a voltage regulator? +
Voltage dividers are best for signal-level applications or voltage sensing, not power delivery. For powering circuits, use a proper voltage regulator. Dividers waste power as heat and their output voltage sags under load.
How do I choose R1 and R2 values? +
Pick values that give your desired ratio while keeping current draw reasonable. Lower resistance means more current (and power waste), higher resistance makes the output more sensitive to loading. A good range is typically 1k to 100k ohms.
How does loading affect a voltage divider? +
Any load connected to Vout acts as a resistor in parallel with R2, effectively lowering R2's value and reducing Vout. For accurate output, the load resistance should be at least 10x greater than R2.
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