Home / Tools / ESP32 ADC Voltage Divider Calculator

ESP32 ADC Voltage Divider Calculator

Given your maximum input voltage and divider resistors, get the ADC pin voltage, raw reading, real resolution and divider power draw — plus a recommended upper resistor value.

Max input voltage (V)

e.g. 12 for a 12 V battery

Upper resistor R1 (kΩ)

Lower resistor R2 (kΩ)

10 kΩ is a good default

ADC reference (V)

usually 3.3

ADC bits

Three truths about the ESP32 ADC

12-bit nominal is not 12-bit accurate: expect roughly 9–10 effective bits. Use an external ADS1115 for precision work.
Default attenuation tops out at 1.1 V: you need 11 dB attenuation to reach ~3.3 V, and linearity gets worse.
ADC2 conflicts with Wi-Fi: on the original ESP32, prefer ADC1 (GPIO 32–39).

Embed this tool

Writing a blog post or answering a forum thread? Embed it — the attribution link comes along automatically.

<iframe src="https://espio.dev/embed/adc/" width="100%" height="640" frameborder="0" loading="lazy" title="adc calculator" style="border:1px solid #e3e6ea;border-radius:10px"></iframe>