esp32 voltage divider readings off
First, ESP32 ADC is 12-bit, not 10-bit. therefore the formula should be:
float voltage = sensorValue * (3.3 / 4096.0);

Secondly, ESP32 ADC is not really linear, and tend to have lower reading than the actual value. You will need to do some calibration if you want to get a more accurate reading. You can take a look at my github on esp32-adc-calibrate.