Convert Fahrenheit to Celsius with JavaScript

By  on  

The United States is one of the last bodies that refuses to implement the Celsius temperature standard. Why? Because we're arrogant and feel like we don't need to change. With that said, if you code for users outside the US, it's important to provide localized weather data to users. Let's took at how you can convert between Fahrenheit and Celsius.

Fahrenheit to Celsius

The formula to convert Fahrenheit to Celsius is:

°C = 5/9 x (°F - 32)

The following function converts Fahrenheit to Celsius:

function convertFahrenheitToCelsius(degrees) {
  return Math.floor(5 / 9 * (degrees - 32));
}

Celsius to Fahrenheit

The formula to convert Celsius to Fahrenheit is:

°F = (°C × 9/5) + 32

The following function converts Celsius to Fahrenheit:

function convertCelsiusToFahrenheit(degrees) {
  return Math.floor(degrees * (9/5) + 32);
}

Temperature conversion is one of those things that's difficult to do in your head due to the somewhat complex formula. If you have a site that reflects weather data, keep these handy functions nearby!

Recent Features

  • By
    5 HTML5 APIs You Didn’t Know Existed

    When you say or read "HTML5", you half expect exotic dancers and unicorns to walk into the room to the tune of "I'm Sexy and I Know It."  Can you blame us though?  We watched the fundamental APIs stagnate for so long that a basic feature...

  • By
    Create a CSS Cube

    CSS cubes really showcase what CSS has become over the years, evolving from simple color and dimension directives to a language capable of creating deep, creative visuals.  Add animation and you've got something really neat.  Unfortunately each CSS cube tutorial I've read is a bit...

Incredible Demos

  • By
    jQuery Countdown Plugin

    You've probably been to sites like RapidShare and MegaUpload that allow you to download files but make you wait a specified number of seconds before giving you the download link. I've created a similar script but my script allows you to animate the CSS font-size...

  • By
    jQuery Wookmark

    The first thing that hits you when you visit Pinterest is "Whoa, the columns are the same width and the photos are cut to fit just the way they should."  Basic web users probably think nothing of it but as a developer, I can appreciate the...

Discussion

  1. The reason the US (and a few other countries) don’t convert to Celsius and other metric systems has nothing to do with arrogance. Do you think that Russia is not arrogant? China? North Korea?

    The reason has to do with cost-benefit analysis. How many mental, economic, medical, social, and legal changes would have to be made, as well as the corresponding costs to time and money, to allow a complete change over. Many efforts have been made to switch the US systems officially to something else and they usually fail because the general public and industry collectively decide, often subconsciously, that it isn’t worth the change.

    To that note, the US is not unique. There are lots of countries that are officially on metric standards, yet still use other units in various places and contexts.

    Additionally, consider time. Time is represented in base 10 units at the low levels, but then it’s base 60 for seconds, base 60 for minutes, base 24 or 12 * 2 for hours, days are sometimes base 30 (but not always), and years are base 12-ish (their size changes from year to year). There have been attempts to use decimal time all around the world, but to date, no country officially uses it. Is the world just arrogant?

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!