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Voltage Divider Calculator

Design a loaded or unloaded resistive voltage divider and select practical preferred resistor values.

Input Parameters

Nearest values used: 10 kΩ and 20 kΩ

Circuit Diagram
3.3 V2.185 V10 kΩ20 kΩ1 MΩ

Equations

Rp=R2∥RL=R2RLR2+RLR_p=R_2\parallel R_L=\dfrac{R_2R_L}{R_2+R_L}
Vout=VinRpR1+RpV_{out}=V_{in}\dfrac{R_p}{R_1+R_p}
Itotal=VinR1+RpI_{total}=\dfrac{V_{in}}{R_1+R_p}
PL=Vout2RLP_L=\dfrac{V_{out}^2}{R_L}
Calculated Values
Input voltage3.3 V
Output voltage2.185 V
R1 used10 kΩ
R2 used20 kΩ
Total circuit current111.457 µA
Total power consumption367.808 µW
RL power consumption4.776 µW

Design guide

Design a voltage divider that remains accurate under load

A voltage divider suits references, measurement inputs, and high-impedance signals. Its output is not a power supply: every load changes the calculated voltage.

Method and assumptions

Unloaded, Vout = Vin·R2/(R1+R2). With a load, replace R2 with R2 in parallel with the load. The calculator exposes this difference so loading error is visible.

Inputs to verify

Input voltage

Use the source’s minimum and maximum range, not only its nominal value.

Load resistance

Enter the real input impedance of the ADC, amplifier, or next circuit, including possible protection paths.

Recommended workflow

  1. 1Set the R1/R2 ratio from the target voltage.
  2. 2Choose resistance values that limit consumption while remaining small relative to the load.
  3. 3Check power, tolerances, noise, and input protection at extremes.

Checkable example

With Vin = 12 V, R1 = 10 kΩ, and R2 = 10 kΩ, the unloaded output is 6 V. If the load is also 10 kΩ, the equivalent lower resistance becomes 5 kΩ and the output falls to 4 V.

Limits to keep in mind

The calculation does not replace a regulator or buffer. Sampled inputs, leakage, tolerance, and temperature can require a lower source resistance.

Frequently asked questions

How should resistor values be chosen?

There is no universal value. Balance consumption, noise sensitivity, leakage current, and loading of the next stage.

Can a voltage divider power a module?

No, except for an extremely small and stable load. Use a suitable regulator when the load varies or draws meaningful current.

References to consult

  • Method reference: Ohm’s law, Thevenin equivalent, and the datasheet for the driven or measured input.

Original educational content, reviewed for technical clarity on 20 August 2026. Always verify datasheets, applicable standards, and your design before power-up or manufacture.