bootstrap/docs/utilities/sizing.md

layout	title	group
docs	Sizing	utilities

Easily make an element as tall (relative to its parent) with our height utilities. Includes support for 25%, 50%, 75%, and 100% by default. Mix and match with our existing grid classes for controlling width.

Height utilities are generated from the $sizes Sass map in _variables.scss. Modify those values as you need to generate different utilities here.

{% example html %}

Height 25%

Height 50%

Height 75%

Height 100%

{% endexample %}

Use max-width: 100%; and max-height: 100%; utilities as needed.

{% example html %} {% endexample %}

{% example html %}

Max-height 100%

{% endexample %}