Answers for "how to change bootstrap spacer to percent"

bootstrap Margin and padding

Use the margin and padding spacing utilities to control how elements and 
components are spaced and sized. Bootstrap 4 includes a five-level scale for
spacing utilities, based on a 1rem value default $spacer variable. Choose
values for all viewports (e.g., .mr-3 for margin-right: 1rem), or pick
responsive variants to target specific viewports (e.g., .mr-md-3 for 
margin-right: 1rem starting at the md breakpoint).

<div class="my-0 bg-warning">Margin Y 0</div>
  <div class="my-1 bg-warning">Margin Y 1</div>
  <div class="my-2 bg-warning">Margin Y 2</div>
  <div class="my-3 bg-warning">Margin Y 3</div>
  <div class="my-4 bg-warning">Margin Y 4</div>
  <div class="my-5 bg-warning">Margin Y 5</div>
  <div class="my-auto bg-warning">Margin Y Auto</div>

bootstrap spacing

The classes are named using the format {property}{sides}-{size} for xs 
and {property}{sides}-{breakpoint}-{size} for sm, md, lg, and xl.

Where property is one of:

m - for classes that set margin
p - for classes that set padding

Where sides is one of:

t - for classes that set margin-top or padding-top
b - for classes that set margin-bottom or padding-bottom
l - for classes that set margin-left or padding-left
r - for classes that set margin-right or padding-right
x - for classes that set both *-left and *-right
y - for classes that set both *-top and *-bottom
blank - for classes that set a margin or padding on all 4 sides of the element

Where size is one of:

0 - for classes that eliminate the margin or padding by setting it to 0
1 - (by default) for classes that set the margin or padding to $spacer * .25
2 - (by default) for classes that set the margin or padding to $spacer * .5
3 - (by default) for classes that set the margin or padding to $spacer
4 - (by default) for classes that set the margin or padding to $spacer * 1.5
5 - (by default) for classes that set the margin or padding to $spacer * 3
auto - for classes that set the margin to auto

$spacer defaults to 1rem