Voltage Divider Calculator
Estimate the unloaded output voltage across the lower resistor of a two-resistor series divider.
How to use this calculator
- Enter input voltage and both positive resistor values.
- Review the worked example for voltage divider calculator and compare the inputs with your own units.
- Change one assumption at a time and recalculate if you need a second scenario.
Ideal divider equation
Vout = Vin × R2 ÷ (R1 + R2), where R2 is the lower resistor connected to the reference node.
- This basic equation assumes a stable input and an output load whose impedance is large compared with R2.
- The result is calculated from the values entered; the page does not independently verify assumptions, data quality or real-world suitability.
Worked examples
Equal resistors
With 12 V input and two equal 10 kΩ resistors, the output sits halfway across the input in the ideal unloaded case.
12 × 10,000 ÷ (10,000 + 10,000) = 6 V.
The ideal output voltage is 6 V.
Understanding the result
The resistor ratio determines the fraction of the input voltage observed at the output.
A real load changes the effective lower resistance; resistor tolerance, power rating, noise and source impedance also matter.
Important notes
Check resistor power dissipation and input limits before building a circuit.
Displayed figures are rounded for readability. Preserve more precision during intermediate calculations and verify the labels and units before using the estimate.
Frequently asked questions
What does the Voltage Divider Calculator show?
The resistor ratio determines the fraction of the input voltage observed at the output.
What assumptions should I check?
Check resistor power dissipation and input limits before building a circuit.
Does this replace expert or authoritative guidance?
A real load changes the effective lower resistance; resistor tolerance, power rating, noise and source impedance also matter.
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Related explanations
Learn the method behind the number or compare the terminology before using the calculator.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.