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
    Chris Coyier’s Favorite CodePen Demos

    David asked me if I'd be up for a guest post picking out some of my favorite Pens from CodePen. A daunting task! There are so many! I managed to pick a few though that have blown me away over the past few months. If you...

  • By
    Camera and Video Control with HTML5

    Client-side APIs on mobile and desktop devices are quickly providing the same APIs.  Of course our mobile devices got access to some of these APIs first, but those APIs are slowly making their way to the desktop.  One of those APIs is the getUserMedia API...

Incredible Demos

  • By
    Spyjax:  Ajax For Evil Using Dojo

    The idea of Spyjax is nothing new. In pasts posts I've covered how you can spy on your user's history with both MooTools and jQuery. Today we'll cover how to check user history using the Dojo Toolkit. The HTML For the sake of this...

  • By
    MooTools Overlay Plugin

    Overlays have become a big part of modern websites; we can probably attribute that to the numerous lightboxes that use them. I've found a ton of overlay code snippets out there but none of them satisfy my taste in code. Many of them are...

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!