int reading = analogRead(A0);
float mv = (reading * 5.0) / 1024.0;
this code results in volts...
try this
int raw = analogRead(tempPin);
float milliVolts = raw * 4.887586; // faster than * 5.0/1023 ==> 0 .. 5000
float tempC = (milliVolts - 500) * 0.05; // faster than / 20 ==> -500 .. 4500 ==> / 20 ==> -25 .. +225
float tempH = tempC * 1.8 + 32;