Need help with converting Celsius to Fahrenheit in the code

Question

I'm new to Arduino and trying to figure out how to convert Celsius to Fahrenheit with the parameters listed below. Do I need to create a separate file for the calculations? If so, can someone help me on how I can go about doing that?

#include <DHT.h>
#include <DHT_U.h>

int SENSOR = 2;
int TEMPERATURE;
int HUMIDITY;

DHT dht(SENSOR, DHT11);

void setup() {
  Serial.begin(9600);
  dht.begin();
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  TEMPERATURE = dht.readTemperature();
  HUMIDITY = dht.readHumidity();
  Serial.print("Temp: ");
  Serial.print(TEMPERATURE);
  Serial.println(" celsius ");
  Serial.println(" ");
  Serial.print("Humidity: ");
  Serial.println(HUMIDITY);
  delay(2000);

  //Built In LED
  digitalWrite(LED_BUILTIN, HIGH);  // turn the LED on (HIGH is the voltage level)
  delay(250); // wait for a second
  digitalWrite(LED_BUILTIN, LOW); // turn the LED off by making the voltage LOW
  delay(250);  
}

Answer 1

If you are using the Adafruit DHT sensor library, then you can get a Fahrenheit reading by passing true as an argument to readTemperature(). C.f. the comment in the source code. For example:

Serial.print("Temp: ");
Serial.print(dht.readTemperature(true));  // true -> Fahrenheit
Serial.println(" deg. F");

Note that this library offers also the conversion functions convertCtoF() and convertFtoC().

Answer 2

You could add a function to your sketch.

// Celsius to Fahrenheit conversion
double Fahrenheit(double celsius){
  return 1.8 * celsius + 32;
}

Then add this code to your loop().

Serial.print("Temp: ");
Serial.print(Fahrenheit(TEMPERATURE));
Serial.println(" fahrenheit ");