In Bootstrap 4, there is an easy way to create equal width columns: just use the .col-size class on a specified number of col elements. Bootstrap will recognize how many columns there are, and each column will get the same width.
.col-size
Two columns: 50% width on all screens, except for extra small (100% width on screens less than 576px wide)
Four columns: 25% width on all screens, except for extra small (100% width on screens less than 576px wide)