Temperature Conversions using Java

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In this article, we’ll see the temperature conversions between four different temperature scales named Fahrenheit, Celsius, Kelvin, and Rankine.

Temperature Scales

Fahrenheit Scale

  • Fahrenheit scale was created by German scientist Daniel Gabriel Fahrenheit
  • According to this scale, water freezes at 32 degrees of Fahrenheit and boils at 212 degrees of Fahrenheit
  • So it will take 180 degrees of Fahrenheit to boil water from its freezing state

Celsius Scale

  • Celsius scale was created by Swedish scientist Anders Celsius
  • According to this scale, water freezes at 0 degrees of Celsius and boils at 100 degrees of Celsius
  • So it will take 100 degrees Celsius to boil water from its freezing state

Kelvin Scale

  • In the 19th century, the Kelvin scale was created by the British scientist William Thompson, who is also called as Lord Kelvin
  • According to the Kelvin scale, water freezes at 273.15 K and boils at 373.15 K
  • So it will take 100 K to boil water from its freezing state

Rankine Scale

  • In the 19th century, the Rankine Scale was created by the Scottish scientist William John Rankine
  • According to Rankine Scale, water freezes at 491.67 degrees Rankine and boils at 671.67 degrees Rankine
  • So it will take 180 degrees of Rankine to boil water from its freezing state

Temperature Conversions

Convert Celsius to Fahrenheit:

  • To convert Celsius to Fahrenheit
    • Multiply the ratio of Fahrenheit to Celsius
      • 100 degrees of Celsius is equaled to 180 degrees of Fahrenheit to boil the water from its frozen state
      • The ratio of Fahrenheit to Celsius can be written as 180/100, reducing it to 9/5
    • Add the freezing temperature of Celsius, that is, 32 ºF
  • Formula to convert Celsius to Rankine: ºR = ºC * 9/5 + 32
	public static double celsiusToFahrenheit(double celsius) {
		return (celsius * 9 / 5) + 32;
	}

Convert Celsius to Kelvin:

  • To convert Celsius to Kelvin, we just need to add freezing temperature of Kelvin to ºC
  • Formula to convert Celsius to Kelvin: K = ºC + 273.15 K
	public static double celsiusToKelvin(double celsius) {
		return celsius + 273.15;
	}

Convert Celsius to Rankine:

  • To convert Celsius to Rankine
    • Multiply the ratio of Rankine to Celsius
      • 100 degrees of Celsius is equaled to 180 degrees of Rankine to boil the water from its frozen state
      • The ratio of Rankine to Celsius can be written as 180/100, reducing it to 9/5
    • Add the freezing temperature of Rankine, that is, 491.67 ºR
  • Formula to convert Celsius to Rankine: ºR = ºC * 9/5 + 491.67
	public static double celsiusToRankine(double celsius) {
		return (celsius * 9 / 5) + 491.67;
	}

Convert Fahrenheit to Celsius:

  • To convert Fahrenheit to Celsius
    • Reduce the freezing temperature of Fahrenheit, that is, 32 from given Fahrenheit degrees
    • Multiply the ratio of Celsius to Fahrenheit
      • 100 degrees of Celsius is equal to 180 degrees of Fahrenheit to boil the water from its frozen state
      • The ratio of Celsius to Fahrenheit can be written as 100/180, reducing it to 5/9
  • Formula to convert Fahrenheit to Celsius: ºC = (ºF – 32) * 5/9
	public static double fahrenheitToCelsius(double fahrenheit) {
		return (fahrenheit - 32) * 5 / 9;
	}

Convert Fahrenheit to Kelvin

  • To convert Fahrenheit to Kelvin
    • Reduce the freezing temperature of Fahrenheit, that is, 32 from given Fahrenheit degrees
    • Multiply the ratio of Kelvin to Fahrenheit
      • 100 degrees of Kelvin is equaled to 180 degrees of Fahrenheit to boil the water from its frozen state
      • The ratio of Kelvin to Fahrenheit can be written as 100/180, reducing it to 5/9
    • Add the freezing temperature of Kelvin, that is, 273.15 K
  • Formula to convert Fahrenheit to Kelvin: K = (ºF – 32) * 5/9 + 273.15
	public static double fahrenheitToKelvin(double fahrenheit) {
		return (fahrenheit - 32) * 5 / 9 + 273.15;
	}

Convert Fahrenheit to Rankine

  • To convert Fahrenheit to Rankine
    • Subtract the freezing temperature of Fahrenheit, that is, 32 from the given Fahrenheit degrees
    • Add freezing temperature of Rankine, that is, 491.67
  • Formula to convert Fahrenheit to Rankine: ºR = (ºF – 32) + 491.67
	public static double fahrenheitToRankine(double fahrenheit) {
		return (fahrenheit - 32) + 491.67;
	}

Convert Kelvin to Celsius

  • To convert Kelvin to Celsius, we just need to subtract the freezing temperature of Kelvin, that is, 273.15 from given Kelvin
  • Formula to convert Kelvin to Celsius: ºC = K – 273.15
	public static double kelvinToCelsius(double kelvin) {
		return kelvin - 273.15;
	}

Convert Kelvin to Fahrenheit

  • To convert Kelvin to Fahrenheit
    • Reduce the freezing temperature of Kelvin, that is, 273.15 from Kelvin degrees
    • Multiply the ratio of Fahrenheit to Kelvin
      • 100 degrees of Kelvin is equal to 180 degrees of Fahrenheit to boil the water from its frozen state
      • The ratio of Fahrenheit to Kelvin can be written as 180/100, reducing it to 9/5
    • Add the freezing temperature of Fahrenheit, that is, 32 ºF
  • Formula to convert Kelvin to Rankine: ºR = (K – 273.15) * 9/5 + 32
	public static double kelvinToFahrenheit(double kelvin) {
		return (kelvin - 273.15) * 9 / 5 + 32;
	}

Convert Kelvin to Rankine

  • To convert Kelvin to Rankine
    • Reduce the freezing temperature of Kelvin, that is, 273.15 from Kelvin degrees
    • Multiply the ratio of Rankine to Kelvin
      • 100 degrees of Kelvin is equaled to 180 degrees of Rankine to boil the water from its frozen state
      • The ratio of Rankine to Kelvin can be written as 180/100, reducing it to 9/5
    • Add the freezing temperature of Rankine, that is, 491.67 ºR
  • Formula to convert Kelvin to Rankine: ºR = (K – 273.15) * 9/5 + 491.67
	public static double kelvinToRankine(double kelvin) {
		return (kelvin - 273.15) * 9 / 5 + 491.67;
	}

Convert Rankine to Celsius

  • To convert Rankine to Celsius
    • Reduce the freezing temperature of Rankine, that is, 491.67 from given Rankine degrees
    • Multiply the ratio of Celsius to Rankine
      • 100 degrees of Celsius is equal to 180 degrees of Rankine to boil the water from its frozen state
      • The ratio of Celsius to Rankine can be written as 100/180, reducing it to 5/9
  • Formula to convert Rankine to Celsius: ºC = (ºR – 491.67) * 5/9
	public static double rankineToCelsius(double rankine) {
		return (rankine - 491.67) * 5 / 9;
	}

Convert Rankine to Fahrenheit

  • To convert Rankine to Fahrenheit
    • Subtract the freezing temperature of Rankine, that is, 491.67 from the given Rankine degrees
    • Add freezing temperature of Fahrenheit, that is, 32
  • Formula to convert Rankine to Fahrenheit: ºF = (ºR – 491.67) + 32
	public static double rankineToFahrenheit(double rankine) {
		return (rankine - 491.67) + 32;
	}

Convert Rankine to Kelvin

  • To convert Rankine to Kelvin
    • Reduce the freezing temperature of Rankine, that is, 491.67 from the given Rankine degrees
    • Multiply the ratio of Kelvin to Rankine
      • 100 degrees of Kelvin is equaled to 180 degrees of Rankine to boil the water from its frozen state
      • The ratio of Kelvin to Rankine can be written as 100/180, reducing it to 5/9
    • Add the freezing temperature of Kelvin, that is, 273.15 K
  • Formula to convert Rankine to Kelvin: K = (ºR – 491.67) * 5/9 + 273.15
	public static double rankineToKelvin(double rankine) {
		return (rankine - 491.67) * 5 / 9 + 273.15;
	}

Full Example

Below is the complete example of calling all these functions in a main function.

package com.techstackjournal;

import java.util.Scanner;

public class TemperatureConversions {

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);

		System.out.println("Enter a number to convert the temperature:");
		double number = scanner.nextDouble();
		scanner.close();

		System.out.printf("\n %.2f Celsius to Fahrenheit = %.2f", number, celsiusToFahrenheit(number));
		System.out.printf("\n %.2f Celsius to Kelvin = %.2f", number, celsiusToKelvin(number));
		System.out.printf("\n %.2f Celsius to Rankine = %.2f", number, celsiusToRankine(number));
		System.out.printf("\n %.2f Fahrenheit to Celsius = %.2f", number, fahrenheitToCelsius(number));
		System.out.printf("\n %.2f Fahrenheit to Kelvin = %.2f", number, fahrenheitToKelvin(number));
		System.out.printf("\n %.2f Fahrenheit to Rankine = %.2f", number, fahrenheitToRankine(number));
		System.out.printf("\n %.2f Kelvin to Celsius = %.2f", number, kelvinToCelsius(number));
		System.out.printf("\n %.2f Kelvin to Fahrenheit = %.2f", number, kelvinToFahrenheit(number));
		System.out.printf("\n %.2f Kelvin to Rankine = %.2f", number, kelvinToRankine(number));
		System.out.printf("\n %.2f Rankine to Celsius = %.2f", number, rankineToCelsius(number));
		System.out.printf("\n %.2f Rankine to Fahrenheit = %.2f", number, rankineToFahrenheit(number));
		System.out.printf("\n %.2f Rankine to Kelvin = %.2f", number, rankineToKelvin(number));

	}

	public static double celsiusToFahrenheit(double celsius) {
		return (celsius * 9 / 5) + 32;
	}

	public static double celsiusToKelvin(double celsius) {
		return celsius + 273.15;
	}

	public static double celsiusToRankine(double celsius) {
		return (celsius * 9 / 5) + 491.67;
	}

	public static double fahrenheitToCelsius(double fahrenheit) {
		return (fahrenheit - 32) * 5 / 9;
	}

	public static double fahrenheitToKelvin(double fahrenheit) {
		return (fahrenheit - 32) * 5 / 9 + 273.15;
	}

	public static double fahrenheitToRankine(double fahrenheit) {
		return (fahrenheit - 32) + 491.67;
	}

	public static double kelvinToCelsius(double kelvin) {
		return kelvin - 273.15;
	}
	
	public static double kelvinToFahrenheit(double kelvin) {
		return (kelvin - 273.15) * 9 / 5 + 32;
	}

	public static double kelvinToRankine(double kelvin) {
		return (kelvin - 273.15) * 9 / 5 + 491.67;
	}

	public static double rankineToCelsius(double rankine) {
		return (rankine - 491.67) * 5 / 9;
	}

	public static double rankineToFahrenheit(double rankine) {
		return (rankine - 491.67) + 32;
	}

	public static double rankineToKelvin(double rankine) {
		return (rankine - 491.67) * 5 / 9 + 273.15;
	}

}

Output:

Enter a number to convert the temperature:
10

 10.00 Celsius to Fahrenheit = 50.00
 10.00 Celsius to Kelvin = 283.15
 10.00 Celsius to Rankine = 509.67
 10.00 Fahrenheit to Celsius = -12.22
 10.00 Fahrenheit to Kelvin = 260.93
 10.00 Fahrenheit to Rankine = 469.67
 10.00 Kelvin to Celsius = -263.15
 10.00 Kelvin to Fahrenheit = -441.67
 10.00 Kelvin to Rankine = 18.00
 10.00 Rankine to Celsius = -267.59
 10.00 Rankine to Fahrenheit = -449.67
 10.00 Rankine to Kelvin = 5.56

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