JavaScript: Convert temperatures to and from celsius, fahrenheit

JavaScript Basic: Exercise-11 with Solution

Write a JavaScript program to convert temperatures to and from celsius, fahrenheit.

JavaScript: Fahrenheit and Centigrade Temperatures:

Fahrenheit and centigrade are two temperature scales in use today. The Fahrenheit scale was developed by the German physicist Daniel Gabriel Fahrenheit . In the Fahrenheit scale, water freezes at 32 degrees and boils at 212 degrees.

The centigrade scale, which is also called the Celsius scale, was developed by Swedish astronomer Andres Celsius. In the centigrade scale, water freezes at 0 degrees and boils at 100 degrees. The centigrade to Fahrenheit conversion formula is:

C = (5/9) * (F - 32)

where F is the Fahrenheit temperature. You can also use this Web page to convert Fahrenheit temperatures to centigrade. Just enter a Fahrenheit temperature in the text box below, then click on the Convert button.

Sample Solution:

JavaScript Code:

// Define a function to convert Celsius to Fahrenheit
function cToF(celsius) {
  // Store the input Celsius temperature in a variable
  var cTemp = celsius;

  // Calculate the equivalent Fahrenheit temperature
  var cToFahr = cTemp * 9 / 5 + 32;

  // Create a message string describing the conversion result
  var message = cTemp + '\xB0C is ' + cToFahr + ' \xB0F.';

  // Log the message to the console
  console.log(message);
}

// Define a function to convert Fahrenheit to Celsius
function fToC(fahrenheit) {
  // Store the input Fahrenheit temperature in a variable
  var fTemp = fahrenheit;

  // Calculate the equivalent Celsius temperature
  var fToCel = (fTemp - 32) * 5 / 9;

  // Create a message string describing the conversion result
  var message = fTemp + '\xB0F is ' + fToCel + '\xB0C.';

  // Log the message to the console
  console.log(message);
}

// Call the cToF function with a Celsius temperature of 60
cToF(60);

// Call the fToC function with a Fahrenheit temperature of 45
fToC(45); 

Output:

60°C is 140 °F.
45°F is 7.222222222222222°C.

Live Demo:

See the Pen JavaScript: Convert temperatures - basic-ex-11 by w3resource (@w3resource) on CodePen.

Explanation:

For an exact conversion (Fahrenheit to Celsius / Celsius to Fahrenheit) the following formulas can be applied :

Fahrenheit to Celsius : (°F − 32) ÷ 1.8 = °C
Celsius to Fahrenheit : (°C × 1.8) + 32 = °F

An approximate conversion between degrees Celsius and degrees Fahrenheit is as follows :

Fahrenheit to Celsius : Subtract 30 and halve the resulting number.
Celsius to Fahrenheit : Double the number and add 30.

Flowchart:

ES6 Version:

// Convert Celsius to Fahrenheit using arrow function
const cToF = (celsius) => {
  const cTemp = celsius;
  const cToFahr = cTemp * 9 / 5 + 32;
  const message = `${cTemp}\xB0C is ${cToFahr} \xB0F.`;
  console.log(message);
};

// Convert Fahrenheit to Celsius using arrow function
const fToC = (fahrenheit) => {
  const fTemp = fahrenheit;
  const fToCel = (fTemp - 32) * 5 / 9;
  const message = `${fTemp}\xB0F is ${fToCel} \xB0C.`;
  console.log(message);
};

// Example usage
cToF(60);
fToC(45);  

Improve this sample solution and post your code through Disqus.

Previous: JavaScript program to calculate multiplication and division of two numbers (input from user).
Next: JavaScript program to get the website URL (loading page).