files/en-us/web/css/reference/values/dimension/index.md
The <dimension> CSS data type represents a {{CSSxRef("<number>")}} with a unit attached to it, for example 10px.
CSS uses dimensions to specify distances ({{CSSxRef("<length>")}}), durations ({{CSSxRef("<time>")}}), frequencies ({{CSSxRef("<frequency>")}}), resolutions ({{cssxref("resolution")}}), and other quantities.
The syntax of <dimension> is a {{CSSxRef("<number>")}} immediately followed by a unit which is an identifier. Unit identifiers are case insensitive.
12px 12 pixels
1rem 1 rem
1.2pt 1.2 points
2200ms 2200 milliseconds
5s 5 seconds
200hz 200 Hertz
200Hz 200 Hertz (values are case insensitive)
12 px The unit must come immediately after the number.
12"px" Units are identifiers and therefore unquoted.
3sec The seconds unit is abbreviated "s" not "sec".
{{Specifications}}
{{Compat}}