Icon dimensions

This tutorial is part of Iconify for Svelte tutorial.

By default, icon height is set to "1em", icon width is changed dynamically based on the icon's width/height ratio.

This makes it easy to change icon size by changing font-size in the stylesheet or in style, just like icon fonts:

svelte<script>
   import Icon from '@iconify/svelte';
</script>

<style>
   /*
       Cannot target component in CSS, target SVG
       instead using Svelte's :global() function
   */
   div :global(svg) {
       font-size: 24px;
       line-height: 1em;
   }

   /*
       Must use :global() because Svelte cannot assign style to a
       component by class name, it can only work with standard HTML tags.
   */
   div :global(.big-icon) {
       font-size: 72px;
   }
</style>

<div>
   <Icon icon="cil:locomotive" />
   <Icon icon="cil:paper-plane" style="font-size: 36px" />
   <Icon icon="cil:truck" class="big-icon" />
</div>


If you want to control icon size with width and height in CSS, see how to remove icon dimensions section below.

Units

Size can be a string with or without units or a number. If value is a number or string without units, it will be treated by browser as pixels.

Examples of 24px icon:

jsx// Number
<Icon icon="mdi:home" height={24} />
// String without units
<Icon icon="mdi:home" height="24" />
// String with units
<Icon icon="mdi:home" height="24px" />
// String with units, font-size is 16px
<Icon icon="mdi:home" height="1.5em" />

Keyword "auto"

Special keyword "auto" sets size to value from viewBox. This makes it easy to render an icon as it was originally designed.

It is enough to set one dimension to "auto", another dimension will be set to "auto" too, unless you specify otherwise.

For example, if viewBox="0 0 24 24" and height is set to "auto", height will be set to 24.

jsx<Icon icon="mdi:home" height="auto" />

Keywords "none" and "unset"

Special keywords "none" and "unset" remove dimensions from generated SVG.

This results in icon without dimensions. You should set icon's width and height in CSS.

It is enough to set one dimension to "unset", another dimension will be set to "unset" too, unless you specify otherwise.

svelte<script>
   import Icon from '@iconify/svelte';
</script>

<div>
   <Icon
       icon="mdi:home"
       height="none"
       style="width: 48px; height: 48px"
   />
</div>


This gives you full control over each icon's dimension separately in CSS instead of controlling them both with font-size.

Sometimes you might also need to add display: block; to CSS for icon to behave correctly.

Setting only width or height

In an example above, all icons only use height.

What happens when only one dimension is set?

• If width is not set, but height is set, width is calculated using icon's width/height ratio.
• If height is not set, but width is set, height is calculated using icon's height/width ratio.
• If no dimensions are set in attributes, height is set to "1em" and width is calculated using icon's width/height ratio. Then icon behaves like a text and can be resized using font-size in stylesheet.

Example

Many icons are square. For such icons if you set one dimension, another dimension will have the same value.

However, there are many icons that are not square. For example, icons imported from icon fonts and Font Awesome.

This is data for fa-regular:address-book:

json{
   "body": "<path d=\"M436 160c6.6 0 12-5.4 12-12v-40c0-6.6-5.4-12-12-12h-20V48c0-26.5-21.5-48-48-48H48C21.5 0 0 21.5 0 48v416c0 26.5 21.5 48 48 48h320c26.5 0 48-21.5 48-48v-48h20c6.6 0 12-5.4 12-12v-40c0-6.6-5.4-12-12-12h-20v-64h20c6.6 0 12-5.4 12-12v-40c0-6.6-5.4-12-12-12h-20v-64h20zm-68 304H48V48h320v416zM208 256c35.3 0 64-28.7 64-64s-28.7-64-64-64s-64 28.7-64 64s28.7 64 64 64zm-89.6 128h179.2c12.4 0 22.4-8.6 22.4-19.2v-19.2c0-31.8-30.1-57.6-67.2-57.6c-10.8 0-18.7 8-44.8 8c-26.9 0-33.4-8-44.8-8c-37.1 0-67.2 25.8-67.2 57.6v19.2c0 10.6 10 19.2 22.4 19.2z\" fill=\"currentColor\"/>",
   "width": 448,
   "height": 512
}

Icon size is 448 x 512

If you do not set any dimensions, height will be set to "1em" and width will be set to 448 / 512 = "0.875em". However, values that have more than 2 numbers after decimal point are rounded up, so actual width will be "0.88em":

html<svg
   xmlns="http://www.w3.org/2000/svg"
   xmlns:xlink="http://www.w3.org/1999/xlink"
   aria-hidden="true"
   focusable="false"
   role="img"
   class="iconify iconify--fa-regular"
   width="0.88em"
   height="1em"
   preserveAspectRatio="xMidYMid meet"
   viewBox="0 0 448 512"
>
   <path d="..." fill="currentColor"></path>
</svg>

If you set width to 56, but do not set height, height will be set to 56 * 512 / 448 = 64:

html<svg width="56" height="64" ...>...</svg>

If you set both values: width to 56 and height to 128, values will be as you set them (also see "Alignment" section below):

html<svg width="56" height="128" ...>...</svg>

Alignment

What if you set both width and height and its ratio doesn't match icon's width/height ratio?

For example, what will happen if icon is 24x24, but you set one dimension to 40 and other dimension to 24?

Using box-shadow to show icon dimensions

jsx<Icon icon="jam:info" width="40" height="24" />
<Icon icon="jam:info" width="24" height="40" />

SVG do not behave like other images. When you set a wrong width/height ratio for other image formats, images get stretched. When you do that for SVG, bounding box is changed and the image is aligned inside that bounding box.

In an example above, one icon is too wide and another icon is too tall. The browser will move icons to center instead of stretching icon.