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Bootstrap 6 Font Size

Font size

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Change the font size of text with numbered stops, named stops, or the paired size-and-leading utilities.

ClassStyles
.fs-1font-size: clamp(1.375rem, 1.375rem + 1.5vw, 2.5rem);
.fs-2font-size: clamp(1.325rem, 1.325rem + 0.9vw, 2rem);
.fs-3font-size: clamp(1.3rem, 1.3rem + 0.6vw, 1.75rem);
.fs-4font-size: clamp(1.275rem, 1.275rem + 0.3vw, 1.5rem);
.fs-5font-size: calc(var(--cui-body-font-size) * 1.25);
.fs-6font-size: var(--cui-body-font-size);
.fs-xsfont-size: calc(var(--cui-body-font-size) * 0.75);
.fs-smfont-size: calc(var(--cui-body-font-size) * 0.875);
.fs-mdfont-size: var(--cui-body-font-size);
.fs-lgfont-size: calc(var(--cui-body-font-size) * 1.25);
.fs-xlfont-size: clamp(1.275rem, 1.275rem + 0.3vw, 1.5rem);
.fs-2xlfont-size: clamp(1.3rem, 1.3rem + 0.6vw, 1.75rem);
.fs-3xlfont-size: clamp(1.325rem, 1.325rem + 0.9vw, 2rem);
.fs-4xlfont-size: clamp(1.375rem, 1.375rem + 1.5vw, 2.5rem);
.fs-5xlfont-size: clamp(1.425rem, 1.425rem + 2.1vw, 3rem);
.fs-6xlfont-size: clamp(1.475rem, 1.475rem + 2.7vw, 3.5rem);
.text-xsfont-size: calc(var(--cui-body-font-size) * 0.75);
line-height: 1.25;
.text-smfont-size: calc(var(--cui-body-font-size) * 0.875);
line-height: var(--cui-body-line-height);
.text-mdfont-size: var(--cui-body-font-size);
line-height: var(--cui-body-line-height);
.text-lgfont-size: calc(var(--cui-body-font-size) * 1.25);
line-height: var(--cui-body-line-height);
.text-xlfont-size: clamp(1.275rem, 1.275rem + 0.3vw, 1.5rem);
line-height: 1.4285714286;
.text-2xlfont-size: clamp(1.3rem, 1.3rem + 0.6vw, 1.75rem);
line-height: 1.3333333333;
.text-3xlfont-size: clamp(1.325rem, 1.325rem + 0.9vw, 2rem);
line-height: 1.2;
.text-4xlfont-size: clamp(1.375rem, 1.375rem + 1.5vw, 2.5rem);
line-height: 1.1;
.text-5xlfont-size: clamp(1.425rem, 1.425rem + 2.1vw, 3rem);
line-height: 1.1;
.text-6xlfont-size: clamp(1.475rem, 1.475rem + 2.7vw, 3.5rem);
line-height: 1;
On this page

Font size

Quickly change the font-size of text. While our heading classes (e.g., .h1–.h6) apply font-size, font-weight, and line-height, these utilities only apply font-size. Sizing for these utilities matches HTML’s heading elements, so as the number increases, their size decreases.

.fs-1 text

.fs-2 text

.fs-3 text

.fs-4 text

.fs-5 text

.fs-6 text

html
<p class="fs-1">.fs-1 text</p>
<p class="fs-2">.fs-2 text</p>
<p class="fs-3">.fs-3 text</p>
<p class="fs-4">.fs-4 text</p>
<p class="fs-5">.fs-5 text</p>
<p class="fs-6">.fs-6 text</p>

The same sizes are also available under named stops, which read better than a number once a scale has more than a handful of steps:

.fs-6xl text

.fs-4xl text

.fs-2xl text

.fs-lg text

.fs-xs text

html
<p class="fs-6xl">.fs-6xl text</p>
<p class="fs-4xl">.fs-4xl text</p>
<p class="fs-2xl">.fs-2xl text</p>
<p class="fs-lg">.fs-lg text</p>
<p class="fs-xs">.fs-xs text</p>

.fs-1 … .fs-6 and the named stops are the same sizes: .fs-1 is .fs-4xl, .fs-2 is .fs-3xl, and so on down to .fs-6, which is .fs-md. The 5xl and 6xl stops sit above the headings — display sizes with no numeric alias.

With line height

.text-* sets the font-size and the line-height that belongs to it, so a heading-sized stop comes with heading leading rather than body leading:

.text-3xl text

.text-lg text

.text-sm text

html
<p class="text-3xl">.text-3xl text</p>
<p class="text-lg">.text-lg text</p>
<p class="text-sm">.text-sm text</p>

Customize the scale by modifying the $font-sizes Sass map. Each stop carries both values, and :root gets a --cui-font-size-* and --cui-line-height-* token per stop, so a stop can also be restyled at runtime:

scss
@each $name, $props in $font-sizes {
  $root-token-defaults: map.set($root-token-defaults, --cui-font-size-#{$name}, map.get($props, "font-size"));
  $root-token-defaults: map.set($root-token-defaults, --cui-line-height-#{$name}, map.get($props, "line-height"));
}

Customizing

Sass maps

Each entry is one stop, pairing a font size with the line height that goes with it: .fs-{key} takes the size alone, .text-{key} takes both. Add a key to define a stop, or set one to null to drop it:

scss
$font-sizes: () !default;
// stylelint-disable-next-line scss/dollar-variable-default
$font-sizes: defaults(
  (
    "xs":  ("font-size": calc(var(--cui-body-font-size) * .75),   "line-height": 1.25),
    "sm":  ("font-size": calc(var(--cui-body-font-size) * .875),  "line-height": var(--cui-body-line-height)),
    "md":  ("font-size": var(--cui-body-font-size),               "line-height": var(--cui-body-line-height)),
    "lg":  ("font-size": calc(var(--cui-body-font-size) * 1.25),  "line-height": var(--cui-body-line-height)),
    "xl":  ("font-size": clamp(1.275rem, 1.275rem + .3vw, 1.5rem),  "line-height": calc(2.5 / 1.75)),
    "2xl": ("font-size": clamp(1.3rem, 1.3rem + .6vw, 1.75rem),     "line-height": calc(3 / 2.25)),
    "3xl": ("font-size": clamp(1.325rem, 1.325rem + .9vw, 2rem),    "line-height": 1.2),
    "4xl": ("font-size": clamp(1.375rem, 1.375rem + 1.5vw, 2.5rem), "line-height": 1.1),
    "5xl": ("font-size": clamp(1.425rem, 1.425rem + 2.1vw, 3rem),   "line-height": 1.1),
    "6xl": ("font-size": clamp(1.475rem, 1.475rem + 2.7vw, 3.5rem), "line-height": 1)
  ),
  $font-sizes
);

Utilities API

Font size utilities are declared in our utilities API in scss/_utilities.scss. Learn how to use the utilities API.

scss
"font-size": (
  property: font-size,
  class: fs,
  // The named stops, plus the numeric keys v5 shipped.
  values: map.merge($font-sizes-legacy, map-get-nested($font-sizes, "font-size"))
),
"text-size": (
  property: (font-size, line-height),
  class: text,
  values: $font-sizes
),