Voltage Divider Calculator
Calculate output voltage from a two-resistor voltage divider. Useful for sensor signal conditioning, ADC input scaling and microcontroller reference circuits.
Last updated: May 2026
Enter Vin, R1 and R2
Useful for signal scaling, ADC inputs and reference taps.
Enter Vin, R1 and R2 to calculate Vout.
Why this calculator is useful
Use this page to estimate the output of a simple two-resistor divider before you build it on the bench or place it in a design. The point is not to replace proper design review. The point is to catch obvious mismatches quickly and keep small electronics tasks moving. That is especially helpful in hobby work, repair work and prototype setups where you want a fast answer without opening a full simulator.
A calculator like this earns its place because it reduces the chance of a simple arithmetic mistake creating a bigger bench problem later. Calculate first, then measure on the real circuit.
Typical use cases
- signal scaling, sensor interfacing and reference voltages
- Reading and sanity-checking datasheet examples
- Confirming values before soldering or ordering parts
The final circuit still depends on tolerances, load conditions and the actual parts in front of you, but a quick page like this gives you a reliable starting point.
Related tools
Frequently Asked Questions
What is a voltage divider and when do I need one?
A voltage divider reduces a high voltage to a lower value using two resistors in series. You need one when you must scale a sensor signal (0–5V) to a microcontroller input (0–3.3V), or create a reference voltage for a comparator, or bias a transistor base. The calculator assumes unloaded operation; real circuits with load current give different results.
How does load current affect the output voltage?
This calculator assumes infinite load impedance (no current drawn). If you connect a load that draws current, the output voltage drops below the calculated value. For example, an ADC input with 1MΩ impedance has negligible effect, but a 10kΩ load draws significant current and reduces Vout. Always account for load resistance when designing precision dividers.
Why can't I use very high resistor values?
High resistances increase susceptibility to noise and leakage currents, and make the divider sensitive to load impedance. A 1MΩ/1MΩ divider is impractical; stick to 1kΩ–100kΩ range where possible. Lower values draw more supply current but are more stable and less affected by parasitic effects or high-impedance loads.
When should I use a voltage divider vs a voltage regulator?
Use a divider for simple analog scaling (sensor interfacing, reference voltages, biasing). Use a regulator for stable power supplies with load current regulation. A divider cannot regulate output voltage under changing loads; a regulator actively maintains voltage. For digital logic or power-hungry circuits, always use a regulator.
How do I handle component tolerance and stability?
Resistors have ±5% or ±1% tolerance, which affects divider ratio directly. A ±5% resistor pair creates ±5–10% output voltage error. For precision dividers (ADC reference, sensor scaling), use ±1% or tighter resistors. Also account for temperature drift: resistors change value with heat. Add a bypass capacitor on the output to reduce high-frequency noise.