Responsive Font Size

Question

I've created a site using the Zurb Foundation 3 grid. Each page has a large h1.

CSS

body {font-size:100%}
/* Headers */
h1 { font-size:6.2em;font-weight:500; }

HTML

<div class="row">
<div class="twelve columns text-center">
<h1> LARGE HEADER TAGLINE </h1>
</div><!-- End Tagline -->
</div><!-- End Row -->

When I resize the browser to mobile size the large font doesn't adjust and causes the browser to include a horizontal scroll to accomodate for the large text.

I've noticed that on the Zurb Foundation 3 Typography example page, the headers adapt to the browser as it is compressed and expanded.

Am I missing something really obvious? How do I achieve this?

Answer 1

The font-size won't respond like this when resizing the browser window. Instead they respond to the browser zoom/type size settings, such as if you press ctrl and + together on the keyboard while in the browser.

Media Queries

You would have to look at using media queries to reduce the font-size at certain intervals where it starts breaking your design and creating scrollbars.

For example, try adding this inside your CSS at the bottom, changing the 320px width for wherever your design starts breaking:

@media only screen and (max-width: 320px) {

   body { 
      font-size: 2em; 
   }

}

Viewport percentage lengths

You can also use viewport percentage lengths such as vw, vh, vmin and vmax. The official W3C document for this states:

The viewport-percentage lengths are relative to the size of the initial containing block. When the height or width of the initial containing block is changed, they are scaled accordingly.

Again, from the same W3C document each individual unit can be defined as below:

vw unit - Equal to 1% of the width of the initial containing block.

vh unit - Equal to 1% of the height of the initial containing block.

vmin unit - Equal to the smaller of vw or vh.

vmax unit - Equal to the larger of vw or vh.

And they are used in exactly the same way as any other CSS value:

.text {
  font-size: 3vw;
}

.other-text {
  font-size: 5vh;
}

Compatibility is relatively good as can be seen here. However, some versions of IE and Edge don’t support vmax. Also, iOS 6 and 7 have an issue with the vh unit, which was fixed in iOS 8.

Answer 2

I've been playing around with ways to overcome this issue, and believe I have found a solution:

If you can write your app for IE9+ and all other modern browsers that support CSS calc(), rem units, and vmin units, you can use this to achieve scaleable text without Media Queries:

body {
  font-size: calc(0.75em + 1vmin);
}

Here is it in action: http://codepen.io/csuwldcat/pen/qOqVNO

Answer 3

In actual original sass not scss you could use below mixins to automatically set paragraph and all headings font-size.

I like it because it much more compact. And quicker to type. Other than that it provides same functionality. Anyway if you still want to stick to new syntax - scss then feel free to convert my sass to scss here: [CONVERT SASS TO SCSS HERE]

Below I give you four sass mixins. You will have to tweak their settings to your needs.

=font-h1p-style-generator-manual() // you dont need use this one those are only styles to make it pretty
=media-query-base-font-size-change-generator-manual() // this mixin sets base body size that will be used by h1-h6 tags to recalculate their size in media query
=h1p-font-size-generator-auto($h1-fs: 3em, $h1-step-down: 0.3, $body-min-font-size: 1.2em, $p-same-as-hx: 6) // here you will set the size of h1 and size jumps between h tags
=config-and-run-font-generator() // this one only calls the other ones

After you finish playing with settings just make a call on one mixin - which is: +config-and-run-font-generator(). See code below and comments for more info.

I guess you could do it automatically for media query like it is done for header tags but we all use different media query so it would not be appropriate for everyone. I use mobile first design approach so this is how I would do that. Feel free to copy and use this code.

COPY AND PASTE THOSE MIXINS TO YOUR FILE

=font-h1p-style-generator-manual()
  body
    font-family: "Source Sans Pro", "Helvetica Neue", Helvetica, Arial, sans-serif // google fonts
    font-size: 100%
    line-height: 1.3em
  %headers
    line-height: 1em
    font-weight: 700
  p
    line-height: 1.3em
    font-weight: 300
  @for $i from 1 through 6
    h#{$i}
      @extend %headers


=media-query-base-font-size-change-generator-manual()
  body
    font-size: 1.2em
  @media screen and (min-width: 680px)
    body
      font-size: 1.4em
  @media screen and (min-width: 1224px)
    body
      font-size: 1.6em
  @media screen and (min-width: 1400px)
    body
      font-size: 1.8em

=h1p-font-size-generator-auto($h1-fs: 3em, $h1-step-down: 0.3, $body-min-font-size: 1.2em, $p-same-as-hx: 6)
  $h1-fs: $h1-fs // set first header element to this size
  $h1-step-down: $h1-step-down // decrement each time by 0.3
  $p-same-as-hx: $p-same-as-hx // set p font-sieze same as h(6)
  $h1-fs: $h1-fs + $h1-step-down // looping correction
  @for $i from 1 through 6
    h#{$i}
      font-size: $h1-fs - ($h1-step-down * $i)
    @if $i == $p-same-as-hx
      p
        font-size: $h1-fs - ($h1-step-down * $i)

// RUN ONLY THIS MIXIN IT WILL TRIGGER THE REST
=config-and-run-font-generator()
  +font-h1p-style-generator-manual() // just a place holder for our font style
  +media-query-base-font-size-change-generator-manual() // just a place holder for our media query font size
  +h1p-font-size-generator-auto($h1-fs: 2em, $h1-step-down: 0.2, $p-same-as-hx: 5) // set all parameters here

CONFIGURE ALL MIXINS TO YOUR NEEDS - PLAY WITH IT! :) AND THEN CALL IT ON THE TOP OF YOUR ACTUAL SASS CODE WITH:

+config-and-run-font-generator()

This would generate this output. You can customize parameters to generate different sets of results, however because we all use different media query some mixins you will have to edit manually (style and media).

GENERATED CSS:

body {
  font-family: "Source Sans Pro", "Helvetica Neue", Helvetica, Arial, sans-serif;
  font-size: 100%;
  line-height: 1.3em;
  word-wrap: break-word; }

h1, h2, h3, h4, h5, h6 {
  line-height: 1em;
  font-weight: 700; }

p {
  line-height: 1.3em;
  font-weight: 300; }

body {
  font-size: 1.2em; }

@media screen and (min-width: 680px) {
  body {
    font-size: 1.4em; } }
@media screen and (min-width: 1224px) {
  body {
    font-size: 1.6em; } }
@media screen and (min-width: 1400px) {
  body {
    font-size: 1.8em; } }
h1 {
  font-size: 2em; }

h2 {
  font-size: 1.8em; }

h3 {
  font-size: 1.6em; }

h4 {
  font-size: 1.4em; }

h5 {
  font-size: 1.2em; }

p {
  font-size: 1.2em; }

h6 {
  font-size: 1em; 

}

Answer 4

There are the following ways by which you can achieve this:

1. Use rem for e.g. 2.3 rem
2. Use em for e.g. 2.3em
3. Use % for e.g. 2.3% Moreover, you can use : vh, vw, vmax and vmin.

These units will autoresize depending upon the width and height of the screen.

Answer 5

There's another approach to responsive font sizes - using rem units.

html {
    /* base font size */
    font-size: 16px;
}

h1 { font-size: 1.5rem; }
h2 { font-size: 1.2rem; }

Later in media queries, you can adjust all fonts sizes by changing base font size:

@media screen and (max-width: 767px) {
  html {
    /* reducing base font size will reduce all rem sizes */
    font-size: 13px;
  }

    /* you can reduce font sizes manually as well*/
    h1 { font-size: 1.2rem; }
    h2 { font-size: 1.0rem; }

}

To make this work in IE7-8 you will have to add a fallback with px units:

h1 {
    font-size: 18px;
    font-size: 1.125rem;
} 

If you're developing with LESS, you can create a mixin that will do the math for you.

Rem units support - http://caniuse.com/#feat=rem

Answer 6

Here is something that worked for me. I only tested it on an iPhone.

Whether you have h1, h2, or p tags put this around your text:

<h1><font size="5">The Text you want to make responsive</font></h1>

This renders a 22pt text on a desktop and it is still readable on the iPhone.

<font size="5"></font>