General EE Utilities
VOLTAGE DIVIDER CALCULATOR
Calculate output voltage for resistive voltage dividers with standard resistor value suggestions.
Design resistive voltage dividers with real-time calculations. Enter your input voltage and resistor values — the calculator shows output voltage, current draw, power dissipation, and suggests the nearest E24 standard resistor values to match your design.
Enter any three known values
Click a field label to mark it as the unknown to solve for.
Results
Enter three values and click Calculate
The field with the orange border will be solved
Formulas Used
This tool can solve for any one unknown (Vin, Vout, R1, or R2) when the other three are provided.
\[V_{out} = V_{in} \times \frac{R_2}{R_1 + R_2}\]
\[V_{in} = V_{out} \times \frac{R_1 + R_2}{R_2}\]
\[R_1 = R_2 \times \frac{V_{in} - V_{out}}{V_{out}}\]
\[R_2 = R_1 \times \frac{V_{out}}{V_{in} - V_{out}}\]
\[I_{divider} = \frac{V_{in}}{R_1 + R_2}\]
Vin = source voltage
Vout = divided output voltage
R1 = top resistor
R2 = bottom resistor to ground.
Understanding Voltage Dividers
A voltage divider is one of the most fundamental circuits in electronics. It consists of two resistors connected in series between a voltage source and ground, with the output voltage taken from the junction between them. The output voltage is a fraction of the input, determined by the ratio of the two resistors. See the Formulas Used section above for the exact equations used by this calculator.
Voltage dividers are used extensively in sensor interfaces, ADC input scaling, bias networks, and reference voltage generation. While simple in concept, proper design requires attention to loading effects — if the load impedance is not significantly higher than R2, the actual output voltage will be lower than the calculated value.
When selecting resistor values, consider the divider current (the quiescent current flowing through R1 and R2). Higher resistance values reduce power consumption but increase susceptibility to noise and loading effects. For most signal-level applications, total divider impedance between 1kΩ and 100kΩ provides a good balance.
For aerospace and defense applications, resistor selection must account for tolerance, temperature coefficient (tempco), and long-term stability. Calpak USA's engineering team can help select military-grade components and validate your voltage reference designs. Contact us for a design review.
Quick Reference: Common Voltage Divider Configurations
Using E24 standard resistor values, Vin = 5V
| Target Vout | R1 | R2 | Actual Vout |
|---|---|---|---|
| 3.3V | 5.1kΩ | 10kΩ | 3.311V |
| 2.5V | 10kΩ | 10kΩ | 2.500V |
| 1.8V | 18kΩ | 10kΩ | 1.786V |
| 1.25V | 30kΩ | 10kΩ | 1.250V |
| 0.5V | 91kΩ | 10kΩ | 0.495V |
Values use E24 standard resistors. Actual voltage depends on resistor tolerance, temperature, and load impedance. Always verify in your specific application.
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