Unloaded V_out
V_out = V_in × R2/(R1+R2)Last updated:
Voltage Divider Calculator
Calculate output voltage for resistor voltage dividers. Design sensor circuits, reference voltages & signal conditioning. Free electronics calculator with sc...
Voltage Divider Calculator
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Professional voltage divider calculator with standard resistor values, tolerance analysis, loading effects, and multi-stage design. Calculate Vout, power dissipation, and impedance.
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Input Voltage
V
Resistor Values
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Electronics & Circuit Design
Voltage Divider Calculator: Resistor Network Design Guide
Calculate output voltage, resistor ratios, current, power dissipation, and loading effects for precision circuit design.
Output Voltage
V_out = V_in × R2/(R1+R2)
Total Resistance
R_total = R1 + R2
Divider Current
I = V_in / R_total
Input Impedance
Z_in = R1 + R2
Reviewed by: CalculatorApp Electronics Engineering Team
What Is a Voltage Divider?
A voltage divider is one of the most fundamental passive circuits: two resistors in series connected across a voltage source produce a lower output voltage at their junction. It is used for level shifting, sensor biasing, ADC input scaling, signal attenuation, and setting reference voltages in analog circuits. Understanding loading effects, Thevenin equivalents, and power ratings is essential for reliable design.
Loaded V_out
V_out = V_in × (R2||R_L)/(R1+R2||R_L)Power (R1)
P1 = I² × R1 = (V_in-V_out)²/R1Thevenin R
R_th = R1 || R2| E-Series | Values per Decade | Tolerance |
|---|---|---|
| E6 | 6 preferred values | 20% |
| E12 | 12 preferred values | 10% |
| E24 | 24 preferred values | 5% |
| E96 | 96 preferred values | 1% |
History Timeline
1845: Gustav Kirchhoff formulates current and voltage laws, establishing the mathematical basis for resistive dividers.
1870s: Wheatstone bridge (an extended divider) becomes the standard for precision resistance measurement.
1900s: Potentiometers (adjustable voltage dividers) widespread in radio volume controls and signal calibration.
1950s: Bipolar transistor circuits use voltage dividers for base bias networks in amplifier design.
1970s: Op-amp virtual ground and gain-setting resistors apply voltage divider principles in integrated circuits.
Modern era: Precision thin-film resistor dividers achieve 0.01% accuracy in high-resolution ADC reference circuits.
IEEE Standards
Electronic circuit design standards from the Institute of Electrical and Electronics Engineers.
IEC Resistor Standards
International standards for fixed resistors and tolerance series.
NIST Electrical Metrology
Precision electrical measurement standards and traceable references.
OSHA Electrical Safety
Workplace electrical safety standards for circuit design.
Myth: A voltage divider can power a load like a regulator.
Fact: Voltage dividers waste significant power and have poor regulation under load. Use a regulator IC for power delivery.
Myth: Output voltage is independent of the connected load.
Fact: Any load in parallel with R2 causes a loading error; lower load impedance causes larger error.
Myth: Tolerance does not matter for voltage dividers.
Fact: For precision applications, a ±1% tolerance on both R1 and R2 can result in ±2% total output error.
Myth: Higher resistor values are always better to save power.
Fact: Very high resistances make dividers sensitive to parasitic capacitance and input bias currents.
FAQ (12)
What is a voltage divider?
A voltage divider uses two series resistors to produce an output voltage that is a fraction of the input voltage: V_out = V_in × R2/(R1+R2).
When does the voltage divider formula become inaccurate?
When the load resistance is comparable to R2 (loading effect), the actual V_out drops below the unloaded formula prediction.
What is the loading effect?
A low-impedance load in parallel with R2 reduces the effective lower resistance and pulls V_out down. The loaded V_out = V_in × (R2||R_L)/(R1 + R2||R_L).
How do I choose resistor values?
Set the divider current (bleeder current) at least 10× the expected load current to minimize loading effect.
What is the input impedance of a voltage divider?
Z_in = R1 + R2. A high-impedance source requires high R values; a low-impedance load requires low R values.
Can a voltage divider supply current efficiently?
No. Unregulated dividers waste power proportional to R1+R2. Use a linear regulator or DC-DC converter for power delivery.
What is a resistive attenuator?
An attenuator is an extended voltage divider designed to reduce signal level by a precise dB, used in RF and audio applications.
What is the Thevenin equivalent of a voltage divider?
V_th = V_in × R2/(R1+R2) and R_th = R1||R2. This connects the divider to load analysis and amplifier input modeling.
How does temperature affect resistors?
Resistor values drift with temperature (ppm/°C). Use matched resistors with identical temperature coefficients for precision dividers.
What is an E12 resistor series?
E12 provides 12 preferred values per decade (e.g., 10, 12, 15, 18, 22…27…33…39…47…56…68…82) with ~10% tolerance.
Can I use a voltage divider as a reference voltage?
Only for very light loads. For stable reference voltages, use a dedicated voltage reference IC (e.g., LM4040, REF02).
What is the power rating needed for resistors?
P = V²/R or P = I²R for each resistor. Choose parts rated at least 2× the calculated power for reliability.
References
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