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CSS CSS Basics (2014) Understanding Values and Units Em and Rem Units

Phillip Rubio
PLUS
Phillip Rubio
Courses Plus Student 1,993 Points

Confused about px to em conversion in CSS

The quiz asks: Create a new rule that targets the h2. The h2's parent element has a font-size value of 16px. Use an em unit to give the h2 a font-size value equivalent to 53px.

... So, If an em is equal to 1px, and the base value of the font-size for the h2’s parent is 16px, then, shouldn’t the equivalent of 53px’s be 3.313em’s if 16x3.313 = 53.008?

style.css
/* Complete the challenge by writing CSS below */

header {
  font-size: 1.8em;
}

.title {
  font-size: 1.625rem;
}

h1 {
  font-size: 5.625rem;
}

h2 {
 font-size: 3.313em; 
}
index.html
<!DOCTYPE html>
<html>
  <head>
    <title>Lake Tahoe</title>
    <link rel="stylesheet" href="page.css">
    <link rel="stylesheet" href="style.css">
  </head>
  <body>
    <header>
      <span class="title">Journey through the Sierra Nevada Mountains</span>
      <h1>Lake Tahoe, California</h1>
    </header>
    <div class="main-content">
      <p>
        Lake Tahoe is one of the most breathtaking attractions located in California. It's home to a number of ski resorts, summer outdoor recreation, and tourist attractions. Snow and skiing are a significant part of the area's reputation.
      </p>
      <a href="#">Find out more</a>
      <h2>Check out all the Wildlife</h2>
      <p>
        As spawning season approaches, the fish acquire a humpback and protuberant jaw. After spawning, they die and their carcasses provide a feast for gatherings of mink, bears, and Bald eagles.
      </p>
      <a href="#">See the Wildlife</a>
      <h3>From Tents to Resorts</h3>
      <p>
        Lake Tahoe is full of wonderful places to stay. You have the ability to sleep in the outdoors in a tent, or relax like a king at a five star resort. Here are our top three resorts:
      </p>
    </div>
    <footer>
      <p>All rights reserved to the state of <a href="#">California</a>.</p>
      <a href="#top">Back to top &raquo;</a>
    </footer>
  </body>
</html>

3 Answers

John Hill
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
John Hill
Front End Web Development Techdegree Graduate 35,236 Points

Hey Phillip, hope this clarifies:

1) An em is a relative unit, so it wouldn't be equal to a px (a fixed unit). It might be easier to think of em & rem as ratios.

2) You're correct in thinking that 16px is the base value to start from, but I'd work the math a little differently. Instead of trying to multiply up to 53px, divide downwards; i.e., 53px/16px. This will give you the em.

Phillip Rubio
Phillip Rubio
Courses Plus Student 1,993 Points

Thanks for clarifying John! I'll put that in my notes. Leandro, Evgeniia, thanks for the help as well!

Leandro Botella Penalva
Leandro Botella Penalva
17,618 Points

Hi Phillip,

You were almost there, however you don't have to round the number.

53px / 16px = 3.3125em

Evgeniia Mas
Evgeniia Mas
4,452 Points

Hello! Divide current element font-size (53px) on base font-size (16px) - you will get 3.3125. If at present you feel confused about this you can check yourself using online-services For example, https://www.w3schools.com/TAgs/ref_pxtoemconversion.asp