Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

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

Posted by Aidan Palmer
Aidan Palmer
5,844 Points

Why use ems? They seem to be a huge problem compare to %'s and rems.

Why have so many different types of scaling units whenever only a few seem to ACTUALLY make sense. It seems like the other units of scale make it much easier to scale and create.

2 Answers

Steven Parker
Steven Parker
231,248 Points
Steven Parker
Steven Parker
231,248 Points

Sometimes you may want to size a container to fit closely to text contents within it, without regard to the window size or the base document font. For this purpose, the "ems" measurement would be very handy.

Ryan Larsen
Ryan Larsen
2,722 Points
Ryan Larsen
Ryan Larsen
2,722 Points

The original question is the same logic that popped into my mind as well. Searching online I found some points that cleared it up a bit further...

Use em units for sizing that should scale depending on the font size of an element other than the root. (I think Steven gives a good real world example of useful application in regards)

Use rem units unless you’re sure you need em units, including on font sizes.

Use rem units on media queries

Don’t use em or rem in multi column layout widths - use % instead.

Don’t use em or rem if scaling would unavoidably cause a layout element to break.