Voltage Divider Calculator

Calculate output voltage from a resistive voltage divider circuit.

By Konstantin Iakovlev · Updated September 2026 · Source: IETF

V
Ω
Ω

Output Voltage

6.000 V

Current

0.600 mA

Details

Vout6.000 V
Division Ratio0.5000
Total Current0.600 mA
Power (R1)3.600 mW
Power (R2)3.600 mW
FormulaVout = Vin × R2 / (R1 + R2)

Use the Voltage Divider Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only. Results are estimates based on the information you provide and the assumptions described on this page.

How It Works

Working out the output of a resistive divider is a routine step when designing sensor interfaces, setting reference voltages, or scaling signals. Dividing voltage cleanly is central to keeping power consumption in check and circuits stable as electronic systems get denser.

Output voltage follows Vout = Vin * (R2 / (R1 + R2)), where Vin is the input voltage to the divider, R1 is the resistor tied to Vin, and R2 is the resistor tied to ground, with Vout measured across it. The relationship comes straight out of Ohm's Law and Kirchhoff's Voltage Law, on the assumption of an ideal voltage source and no load drawing from Vout.

A divider is meant for signal scaling or setting a reference, not for supplying meaningful current, so treating it as a power supply leads to trouble. The most frequent oversight is ignoring a load on Vout, which sits in parallel with R2 and pulls the output away from the calculated value. Where real current or tight regulation is needed, a voltage regulator is the right tool rather than a plain divider.

Example: Scaling a 5 V Sensor Output for a 3.3 V ADC

  1. 1 A sensor outputs up to 5 V, but the microcontroller's analog-to-digital converter (ADC) accepts at most 3.3 V, so the signal has to be scaled down.
  2. 2 R1 = 10 kΩ and R2 = 20 kΩ would give 5 × 20 / (10 + 20) = 3.333 V, which is above the 3.3 V limit, so choose R2 = 18 kΩ instead.
  3. 3 Vout = 5 × 18,000 / (10,000 + 18,000) = 5 × 0.6429 = 3.214 V. The calculator also shows the divider current, 5 V / 28 kΩ = 0.179 mA, and the power in each resistor: 0.319 mW in R1 and 0.574 mW in R2.
  4. 4 3.214 V leaves 0.086 V of margin below 3.3 V with no load on Vout. Anything connected to Vout sits in parallel with R2 and pulls the voltage down: a 180 kΩ load (10 × R2) would lower it to about 3.103 V, so check the ADC's input impedance against R2.

Source: IETF · Last updated: September 2026

Frequently Asked Questions

How does a voltage divider work?
A voltage divider uses two resistors in series to create an output voltage that is a fraction of the input. Output voltage = Vin x R2/(R1+R2). For example, with R1=1kΩ, R2=2kΩ, and 9V input, output is 6V.
When should you use a voltage divider?
Voltage dividers are used for sensor signal conditioning, reference voltage generation, level shifting, and reading analog voltages. They work best with high-impedance loads that draw minimal current.
Why does loading affect voltage divider output?
Connecting a load in parallel with R2 effectively reduces the bottom resistance, lowering the output voltage. For accurate results, the load impedance should be at least 10x greater than R2.

You might also need

Password Strength Checker

Check password strength, entropy, and estimated crack time. Get suggestions for stronger passwords.

IP Subnet Calculator

Calculate network address, broadcast, usable hosts, and wildcard mask from IP and CIDR notation.

Download Time Calculator

Estimate file download time at different connection speeds. Compare across 10Mbps to 1Gbps.