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Setting font size

From: CSS: Core Concepts

Video: Setting font size

To control the size of your fonts you'll use the aptly named font size property. You know for the most part controlling the size of text is pretty straight forward, but there are some things to consider when deciding on which unit of measurement to use. So I want to take a look at not only the property but those considerations as well. Let's go ahead and open up the font-size.htm and you can find that in the 04_03 folder. Pretty basic page, kind of somewhat what we've been using before, we have an article with a heading and a couple paragraphs inside of it and not much else going on. And then we have some basic generic styles going on up in the head of the document.

Setting font size

To control the size of your fonts you'll use the aptly named font size property. You know for the most part controlling the size of text is pretty straight forward, but there are some things to consider when deciding on which unit of measurement to use. So I want to take a look at not only the property but those considerations as well. Let's go ahead and open up the font-size.htm and you can find that in the 04_03 folder. Pretty basic page, kind of somewhat what we've been using before, we have an article with a heading and a couple paragraphs inside of it and not much else going on. And then we have some basic generic styles going on up in the head of the document.

So I want to focus on the heading and the paragraph first and take a look at using the font-size property. I am just going to create a new rule for heading one and inside that I want to use font-size and I want to set that to a value 24 pixels. I will do the same thing for my paragraph. I will create a paragraph rule, and we will do font-size, and let's take that to 16 pixels. So if I Save this and I preview this in one of my browsers, there is my text sized exactly the way that I wanted it to.

Right now, it's using the sort of absolute value of pixels, but there are a lot of different units of measurement that you can use for this. So if I go back to my code, one of the first things I want to explore is using keywords. So there are reserve keywords for font- size and it starts all the way down at xx-small, it goes all the way up to xx large. So if I am on h1 I could do xx-large for heading one, and for paragraphs we will do xx-small. So if I Save this, go back to my page and preview that, you can see the relationship that I have got here now, very large heading, very small text sizing.

This goes all the way from x-large to x- small, then we have large and small and then finally we just have medium in terms of reserve keywords. You can see they are exactly the same size, we just have our heading Bold at the moment. So essentially we have xx small, x small, small, medium large, x large and xx large. There are 7 reserved keywords and if you are one of those people that can remember all the way back to using the font tag in the early days of HTML, we had a font-size property, that we could set a number between one and seven.

There's a little bit of correspondence between those keywords and sort of those reserved size for fonts. Essentially, the specification recommends a scaling factor from one keyword to another. So it's really up to the user agents to determine what size to make these. So don't expect them to be the same size in every single browser, if you start using those keywords. Okay I want to take a look, we have used some absolute values and we have used some reserve keywords. I want to take a look at using relative units of measurement. Now we all know browsers have default style sheets that apply.

So the h1 and the paragraph elements, those already have a default size that is set within the browser. Any time I use this property I am overriding that. Well the default size that they have within the browsers is using a relative unit of measurement like ems. I want to take a look at how ems work. So if I go to my font-size for my heading and I say 1.8em and for paragraph I say 1em, if I save this and preview this on my browser again, I get the sort of relationship between my text. My heading is a good bit larger 1.8 times what my paragraph would be because my paragraph is at 1em.

1em is essentially telling the user agent, okay, just give me whatever your default font size may be. 1.8em is the headings way of saying, well give me slightly larger than that. Give me 1.8 times what that would be. So that value is going to be calculated. Now the value is calculated based on the parent element wherever the font size of the parent element may be. Since we don't have a font-size set on body, what our header and paragraph are doing is, they are just going after the user agent and saying, okay, I didn't see any font-sizes set what are your default sizes? Now we can change that, if I go into the body, for example, and I choose to apply a font-size here, I have a couple of options.

One, I could use a relative unit of measurement. Now if I did that, let's say I do something like 2em and I save this and I preview it. We still have the same relationship but man, it is a lot bigger right. Well the reason that this happens with the body when it uses the relative unit of measurement, it is first going out to the user agent and it's saying what's your default font size? For most browsers, the default font size is initially set to 16 pixels unless the user changes it that's pretty much where it sits. So as a designer you can use that size as more of a baseline for sizing your text.

So 2em is basically saying okay the default font-size is 36 pixels. That 36 pixels is being passed down to our paragraph, and then the heading is getting 1.8 times that. Maybe a better way to look at working with body is to use percentages instead. So if I come into body and I use say 120 % and I save and I test that and that's essentially again asking the user agent, hey, give me whatever your default font size is, give me 120% of that.

That also means that if I lower that and I go to say 90%, Save that, everything sort of scales down. This is the beauty of using ems. Whether it's the user scaling things up or down or whether it's in this case the body tags scaling things up or down, the relationship between these two elements remains the same. That means that whether you're looking at this on a mobile device or looking at it on a desktop browser the relationship between those two elements size wise is exactly the same. Now I mentioned that users have just as much control over this.

So if I get rid of the font-size on the body and Save this, and I go back to my browser again, it's giving the default font-size from the user agent itself. If I go into my Preferences and I go into the content tab notice that I have a default font and I have a default size and that is indeed set to 16 pixels. Well if I'm having a hard time reading the page, I might go in and change that default, so if I grab this and I go up to say 20 pixels, notice that the fonts on the page immediately change and scale up a little bit to represent that. If I go down and size it scales down accordingly as well.

So that's one of the other great things about using a relative unit of measurement like ems if the user has their user agent set to a larger or smaller size based on their personal preferences while the size of the text might change the relationship between the elements won't. So again, font-size property pretty easy to use, no really weird syntax going on there but when developing a sizing strategy for your site you need to think about whether you want to use a absolute size like those pixels or use relative units of measurement like we are using here to establish relationships between the elements while letting the body selector or the device itself define that baseline font-size.

There isn't really one answer for that it's all going to depend upon the specific goals of each project.

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This video is part of

Image for CSS: Core Concepts
CSS: Core Concepts

81 video lessons · 43463 viewers

James Williamson
Author

 
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  1. 4m 57s
    1. Welcome
      55s
    2. Using the exercise files
      4m 2s
  2. 1h 7m
    1. Exploring default styling
      4m 56s
    2. CSS authoring tools
      2m 29s
    3. CSS syntax
      4m 45s
    4. Writing a selector
      4m 10s
    5. Setting properties
      8m 40s
    6. Common units of measurement
      7m 47s
    7. Inline styles
      5m 1s
    8. Embedded styles
      5m 19s
    9. Using external style sheets
      10m 34s
    10. Checking for browser support
      8m 48s
    11. Dealing with browser inconsistencies
      5m 30s
  3. 2h 15m
    1. Structuring HTML correctly
      2m 51s
    2. Element selectors
      4m 52s
    3. Class selectors
      6m 4s
    4. ID selectors
      3m 27s
    5. Using classes and IDs
      10m 7s
    6. Element-specific selectors
      4m 35s
    7. The universal selector
      5m 42s
    8. Grouping selectors
      4m 49s
    9. Descendent selectors
      7m 32s
    10. Child selectors
      5m 7s
    11. Adjacent selectors
      5m 30s
    12. Attribute selectors
      12m 43s
    13. Pseudo-class selectors
      3m 54s
    14. Dynamic pseudo-class selectors
      8m 29s
    15. Structural pseudo-class selectors
      6m 45s
    16. Nth-child selectors
      13m 10s
    17. Pseudo-element selectors
      12m 40s
    18. Targeting page content: Lab
      8m 56s
    19. Targeting page content: Solution
      7m 59s
  4. 42m 39s
    1. What happens when styles conflict?
      4m 0s
    2. Understanding the cascade
      5m 47s
    3. Using inheritance
      6m 11s
    4. Selector specificity
      6m 55s
    5. The !important declaration
      4m 5s
    6. Reducing conflicts through planning
      3m 33s
    7. Resolving conflicts: Lab
      6m 45s
    8. Resolving conflicts: Solution
      5m 23s
  5. 1h 47m
    1. Setting a font family
      7m 10s
    2. Using @font-face
      9m 18s
    3. Setting font size
      7m 35s
    4. Font style and font weight
      6m 52s
    5. Transforming text
      3m 58s
    6. Using text variants
      2m 49s
    7. Text decoration options
      4m 26s
    8. Setting text color
      3m 2s
    9. Writing font shorthand notation
      8m 49s
    10. Controlling text alignment
      6m 33s
    11. Letter and word spacing
      9m 11s
    12. Indenting text
      4m 30s
    13. Adjusting paragraph line height
      10m 30s
    14. Controlling the space between elements
      6m 41s
    15. Basic text formatting: Lab
      8m 45s
    16. Basic text formatting: Solution
      7m 14s
  6. 2h 1m
    1. Understanding the box model
      16m 53s
    2. Controlling element spacing
      14m 29s
    3. Controlling interior spacing
      10m 49s
    4. Margin and padding shorthand notation
      6m 27s
    5. Adding borders
      8m 57s
    6. Defining element size
      10m 7s
    7. Creating rounded corners
      6m 58s
    8. Background properties
      2m 51s
    9. Using background images
      5m 10s
    10. Controlling image positioning
      10m 25s
    11. Using multiple backgrounds
      7m 5s
    12. Background shorthand notation
      5m 25s
    13. Styling container elements: Lab
      7m 55s
    14. Styling container elements: Solution
      8m 17s
  7. 47m 51s
    1. Color keyword definitions
      5m 4s
    2. Understanding hexadecimal notation
      6m 5s
    3. Using RGB values
      4m 58s
    4. Using HSL values
      5m 17s
    5. Working with opacity
      2m 23s
    6. Using RGBa and HSLa
      3m 8s
    7. Styling drop shadows
      5m 38s
    8. CSS gradients
      6m 32s
    9. Working with color: Lab
      4m 26s
    10. Working with color: Solution
      4m 20s
  8. 1m 58s
    1. Additional resources
      1m 58s

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