line-height

The line-height CSS property sets the amount of space used for lines, such as in text. On block-level elements, it specifies the minimum height of line boxes within the element. On non-replaced inline elements, it specifies the height that is used to calculate line box height.

/* Keyword value */
line-height: normal;

/* Unitless values: use this number multiplied
by the element's font size */
line-height: 3.5;

/* <length> values */
line-height: 3em;

/* <percentage> values */
line-height: 34%;

/* Global values */
line-height: inherit;
line-height: initial;
line-height: unset;

Syntax

The line-height property is specified as any one of the following:

• a <number>
• a <length>
• a <percentage>
• the keyword normal.

Values

normal

Depends on the user agent. Desktop browsers (including Firefox) use a default value of roughly1.2, depending on the element's font-family.

<number>

The used value is this unitless <number> multiplied by the element's own font size. The computed value is the same as the specified <number>. In most cases, this is the preferred way to set line-height and avoid unexpected results due to inheritance.

<length>

The specified <length> is used in the calculation of the line box height. Values given in em units may produce unexpected results (see example below).

<percentage>

Relative to the font size of the element itself. The computed value is this <percentage> multiplied by the element's computed font size. Percentage values may produce unexpected results (see the second example below).

Formal syntax

normal | <number> | <length> | <percentage>

Examples

Basic example

/* All rules below have the same resultant line height */

div { line-height: 1.2;   font-size: 10pt; }   /* number */ 
div { line-height: 1.2em; font-size: 10pt; }   /* length */ 
div { line-height: 120%;  font-size: 10pt; }   /* percentage */
div { font: 10pt/1.2  Georgia,"Bitstream Charter",serif; } /* font shorthand */

It is often more convenient to set line-height by using the font shorthand as shown above, but this requires the font-family property to be specified as well.

Prefer unitless numbers for line-height values

This example shows why it is better to use <number> values instead of <length> values. We will use two <div> elements. The first, with the green border, uses a unitless line-height value. The second, with the red border, uses a line-height value defined in ems.

CSS

.green {
  line-height: 1.1;
  border: solid limegreen;
}

.red {
  line-height: 1.1em;
  border: solid red;
}

h1 {
  font-size: 30px;
}

.box {
  width: 18em;
  display: inline-block;
  vertical-align: top;
  font-size: 15px;
}

HTML

<div class="box green">
 <h1>Avoid unexpected results by using unitless line-height.</h1>
  length and percentage line-heights have poor inheritance behavior ...
</div>

<div class="box red">
 <h1>Avoid unexpected results by using unitless line-height.</h1>
  length and percentage line-heights have poor inheritance behavior ...
</div>

<!-- The first <h1> line-height is calculated from its own font-size   (30px × 1.1) = 33px  --> 
<!-- The second <h1> line-height results from the red div's font-size  (15px × 1.1) = 16.5px,  probably not what you want -->

Result

Specifications

Browser compatibility

See also

• font, font-size