Calculate the output voltage in a voltage divider circuit using input voltage and resistor values.
Formula:
Vout = Vin × (R2 / (R1 + R2))Welcome to our comprehensive Voltage Divider Calculator page. Voltage dividers are fundamental circuits in electronics, used to scale input voltages down to desired levels. Whether you’re designing sensor interfaces, bias networks, or simple reference circuits, understanding and calculating divider behavior is critical. Our interactive calculator takes two resistor values and an input voltage to instantly compute the output voltage, loaded voltage, and ideal resistor choices for your application.
A voltage divider is a linear circuit made of two series resistors (R1 and R2) connected across a voltage source (Vin). The junction between the resistors provides a fraction of the input voltage, given by:
Where:
Voltage dividers are versatile building blocks in:
Dividers are passive and cannot source significant current; output voltage changes with load. For applications requiring low impedance or driving heavy loads, use buffer amplifiers.
Our user-friendly interface guides you through four simple steps to obtain accurate results:
Specify the supply voltage driving the divider. Supports volts (V), millivolts (mV), and custom units.
Enter R1 and R2 in ohms (Ω), kiloohms (kΩ), or megohms (MΩ). The calculator normalizes units automatically.
If your divider drives a load (RL), include its resistance. The tool computes the loaded output voltage using the parallel combination of R2 and RL.
Instantly receive:
Real‐world dividers often drive ADCs or sensor inputs with finite input impedance. Ignoring load can introduce error.
This assumes no current drawn from the output node.
Define Req = (R2 ∥ RL) = (R2 × RL) / (R2 + RL). Then:
With Vin = 12 V, R1 = 10 kΩ, R2 = 5 kΩ, and RL = 100 kΩ:
Req = (5k × 100k) / (5k + 100k) ≈ 4.76 kΩ
Vout,loaded = 12V × (4.76k / (10k + 4.76k)) ≈ 3.89 VCompared to the ideal 4 V, loading causes a –2.8% drop. Ensure RL ≫ R2 to minimize error.
Follow these recommendations to build reliable voltage divider networks:
Balance between divider impedance and power consumption:
Select total series resistance between 10 kΩ and 100 kΩ for general‐purpose circuits. Adjust for specific noise, source impedance, and power budgets.
Use precision resistors (≤50 ppm/°C) in critical applications to maintain stable output across temperature variations.
Each resistor dissipates power as heat. Calculate dissipation to select suitable resistor wattage ratings:
For 5 V input, R1 = 10 kΩ and R2 = 10 kΩ (Vout = 2.5 V):
PR1 = (5 – 2.5)² / 10k ≈ 0.625 mW
PR2 = (2.5)² / 10k ≈ 0.625 mWChoose resistors rated for at least 4× the calculated dissipation for reliable operation.
Voltage dividers are ubiquitous across electronics:
Dividers map higher voltage signals (e.g., 0–30 V) into microcontroller ADC ranges (0–3.3 V). Ensure divider impedance ≪ ADC input impedance (≥10 kΩ) to avoid measurement error.
Scaling a 0–24 V sensor to 0–3 V for a 12‐bit ADC:
Ratio = 3 / 24 = 0.125 → R2 / (R1 + R2) = 0.125
Choose R1 = 56 kΩ, R2 = 8 kΩADC sees 0–3 V proportionally, preserving 4096 levels across sensor range.
Add a unity‐gain buffer (op‐amp follower) to isolate divider from ADC input variations.
Create stable base‐emitter voltages using divider networks, ensuring correct operating point for amplifiers.
Biasing an NPN transistor at 1 mA collector current requires ~1.2 V base voltage; pick R1 and R2 accordingly from a 12 V rail.
Use divider output into base through base‐emitter resistor; account for base current by making divider source impedance ≪ β × RE.
Include emitter degeneration resistor to mitigate VBE drift with temperature.
Resistor tolerances introduce output voltage variation. Worst‐case error can be estimated by:
Where tol is the resistor tolerance (e.g., 1%, 0.1%).
Perform statistical analysis by sampling resistor values within tolerance bands to predict distribution of Vout.
Use precision resistors (0.1% or better) and trim potentiometers for fine‐tuning.
Developers can integrate our Voltage Divider Calculator via REST API for automated design tools:
POST /api/divider with JSON payload:
{
"Vin": 12,
"R1": 10000,
"R2": 5000,
"RL": 100000
}{
"Vout_ideal": 4,
"Vout_loaded": 3.89,
"Rth": 3333,
"P_R1": 0.0072,
"P_R2": 0.0048
}Embed in PCB design scripts, online BOM generators, or educational platforms to demonstrate divider behavior dynamically.
Secure API access with API keys or OAuth tokens; supports rate limiting for fair usage.
No. Voltage dividers have high output impedance; heavy loads distort output. Use buffer amplifiers or dedicated regulators for loads drawing >1/10 of divider current.
Compute power as V²/R and select resistors rated ≥4× dissipation. For high‐power dividers, use wirewound or metal‐film resistors with adequate thermal mass.
Replace R2 with a potentiometer to allow continuous adjustment of Vout. Limit total resistance to maintain stability and minimize noise.
Resistor values drift with temperature. Use low‐TC parts and include temperature compensation networks if precise voltage references are required.
Only with precision resistors (≤0.01% tolerance) and careful layout to minimize noise and leakage. For highest stability, consider dedicated voltage reference ICs.
Our Voltage Divider Calculator empowers you to design, analyze, and optimize resistor-divider networks with confidence. From simple bias generators to complex sensor interfaces, accurate divider calculations ensure reliable voltage scaling and signal integrity. Bookmark this page, integrate our API into your workflow, and leverage best practices outlined here to achieve precise, stable divider circuits in all your electronic designs.
In some applications, a single voltage divider cannot provide all required voltage levels or maintain precision across a wide dynamic range. Multi-stage divider networks cascade two or more divider pairs to generate multiple reference voltages from one source. Each stage can be tuned independently, allowing:
For an input of ±15 V requiring ±5 V and ±2.5 V rails:
Place a unity-gain op-amp between the first and second divider to prevent the second stage from loading the first, ensuring each output remains stable under varying loads.
Calculate total quiescent current: Itotal ≈ Vin / (R1+R2) + Vfirst_out / (R3+R4). Ensure supply can source this steady current.
Keep divider traces short and use ground planes to minimize pickup of electromagnetic interference between stages.
When resistors are mounted far from measurement circuits or carry significant currents, lead and contact resistance can introduce errors. Four-wire (Kelvin) sensing eliminates this by separating the force and sense connections:
Use four-pin resistor packages or terminal strips with separate screw terminals for force and sense. Route sense wires directly to the ADC or instrumentation amplifier to ensure milliohm-level accuracy.
Short the resistor under test and measure offset voltage to characterise system zero. Subtract this offset from subsequent measurements to correct residual errors.
Precision divider in high-accuracy temperature measurement modules, where a 0.01% error translates to significant temperature drift.
Employ metal-foil or wirewound precision resistors with matched temperature coefficients to maintain stability over wide temperature ranges.
Resistor values drift with temperature, changing the divider ratio. Temperature compensation networks mitigate this effect by combining positive-TC (temperature coefficient) and negative-TC resistors:
To stabilize a 10 kΩ divider resistant to ±50 ppm/°C drift:
Place resistors close together on the PCB to ensure they share the same temperature environment and minimize gradients.
Temperature networks add complexity and size; evaluate if simpler active regulation (e.g., bandgap reference) might suffice.
Subject assembled divider to thermal chamber cycling and record Vout variation to validate performance.
High-value resistors introduce Johnson (thermal) noise, which can degrade low-level signal measurements. Noise spectral density is √(4kTR), where:
Reduce R1 and R2 values where possible, at the expense of higher current draw. Alternatively, add a low-noise buffer amplifier with optimal input impedance to isolate the divider.
Include RC low-pass filters at the output node: Cfilt = 1/(2πRthfc), targeting cutoff below the noise band of interest.
For a 10 kΩ/10 kΩ divider and desired 100 Hz cutoff: C = 1/(2π × 5 kΩ × 100 Hz) ≈ 0.318 μF.
Large capacitors can introduce leakage and phase shift; choose C0G/NP0 dielectric types for stability.
Proper PCB layout ensures divider accuracy by minimizing parasitic effects:
For resistances >100 kΩ, guard rings tied to the output node around the divider traces prevent leakage currents across the PCB surface.
Draw a narrow copper ring around each resistor pad connected to Vout using a 0.2 mm clearance to isolate from other nets.
Specify PCB cleanliness and conformal coating options, since moisture and flux residue increase leakage.
Measure insulation resistance between the guard ring and adjacent nets to ensure >10 GΩ.
When variable divider ratios are required, digital potentiometers (digipots) offer programmable resistance without mechanical wipers. Common interfaces include I²C, SPI, and Up/Down control:
Use a buffer amplifier to isolate the digipot from heavy loads and supply its required reference voltage rails (often VCC). Protect against transient voltages beyond the allowed wiper range.
Implement calibration routines to correct for digipot taper errors by storing LUTs in microcontroller flash.
Automated contrast control in LCD panels, adaptive gain setting in signal chains, and programmable sensor offset calibration.
Digital potentiometers typically handle small currents (≤1 mA); for higher current, place a transistor buffer stage or use custom resistor arrays.
Before hardware prototyping, model your divider network in a SPICE-based simulator (LTspice, PSpice, etc.). Include resistor tolerances, parasitic capacitances, and load conditions:
Define R1 and R2 with .step param statements for tolerance range. Add .noise and .tf commands to analyse noise contribution and transfer function.
R1 in out 10k
R2 out 0 5k
Vin in 0 DC 12
Cfilter out 0 0.1uF
.op
.noise V(out) Vin 1
Check V(out) DC value, noise density, and bandwidth limitations. Iterate on component choices as needed.
Export simulation plots and annotate critical points for inclusion in design reviews and datasheets.