Eps32 Voltmeter is measuring incorrectly. For example, when the voltage is 12.00, it is 10.50. Measures -1.5 volts

I did a voltmeter with the Esp32, but 1.4 volts is missing measurement, I know how to fix it.
1k 10k.
can you help me

#define analogInput 36

float vout = 0.0;
float vin = 0.0;
float value = 0;
float R1 = 10000;
float R2 = 1000;
void setup() {

pinMode(analogInput, INPUT);


void loop() {
value = analogRead(analogInput);

  vout = (value * 3.3) / 4096.0;
  vin = vout / (R2 / (R1 + R2));



Hello, do yourself a favour and please read How to get the best out of this forum and modify your post accordingly (including code tags and necessary documentation of your ask).

I don't. The ESP32 is not famous for its precise ADC.

Thank you for your help