| unit | description | usage |
|---|---|---|
| em | Relative to the font-size of the element (2em means 2 times the size of the current font) | |
| ex | Relative to the x-height of the current font (rarely used) | |
| ch | Relative to the width of the “0” (zero) | |
| rem | Relative to font-size of the root element | |
| vw | Relative to 1% of the width of the viewport* | |
| vh | Relative to 1% of the height of the viewport* | |
| vmin | Relative to 1% of viewport’s* smaller dimension | |
| vmax | Relative to 1% of viewport’s* larger dimension | |
| % | Relative to the parent element |