Celsius to Fahrenheit Conversion in Java

The formula for converting temperature in Celsius to Fahrenheit is,

Fahrenheit = (9/5) * Celsius + 32

For example, if the temperature is 35 in Celsius, the equivalent value in Fahrenheit is (9/5) * 35 + 32 = 95 F.

The formula for converting temperature in Fahrenheit to Celsius is,

Celsius = (5/9) * (Fahrenheit – 32)

For example, if the temperature is 95 in Fahrenheit, the equivalent value in Celsius is (5/9)* (95-32) = 35.

The following table is a conversion table between Celsius and Fahrenheit values (some values are approximate)

Celsius (C) Fahrenheit (F)
100 212
40 104
37 98.6
30 86
21 70
10 50
0 32
-18 0
-40 -40

 

Java Program to Convert Celsius to Fahrenheit

The following Java program converts the user entered temperature value in Celsius to Fahrenheit,

// Celsius to Fahrenheit conversion in Java
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class CelsiusToFahrenheit {
    
    public static void main(String[] args) throws IOException{
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Please enter temperature in Celsius : ");
        double celsius = Double.parseDouble(reader.readLine());
        double fahrenheit = (9.0/5.0)*celsius + 32;
        System.out.println("Temperature in Fahrenheit is : "+fahrenheit);
    }
}

Note the use of double values 9.0 and 5.0. If we use 9 and 5, the results would be wrong since 9/5 would evaluate to an integer.

Java Program to Convert Fahrenheit to Celsius

The following Java program converts the user entered temperature value in Fahrenheit to Celsius ,

// Fahrenheit to Celsius conversion in Java
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class FahrenheitToCelsius {
    public static void main(String[] args) throws IOException{
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Please enter temperature in Fahrenheit : ");
        double fahrenheit = Double.parseDouble(reader.readLine());
        double celsius = (5.0/9.0)*(fahrenheit - 32);
        System.out.println("Temperature in Celsius is : "+celsius);
    }
}

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One Response to “Celsius to Fahrenheit Conversion in Java”

  1. How do we combine the two programs together so that user can ask to convert Fahrenheit to Celsius or Celsius to Fahrenheit?

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