Seven Equal Columns in bootstrap.

cols.css

@media (min-width: 768px) {
  .seven-cols .col-md-1,
  .seven-cols .col-sm-1,
  .seven-cols .col-lg-1  {
    width: 100%;
  }
}

@media (min-width: 992px) {
  .seven-cols .col-md-1,
  .seven-cols .col-sm-1,
  .seven-cols .col-lg-1 {
    width: 14.285714285714285714285714285714%;
  }
}

@media (min-width: 1200px) {
  .seven-cols .col-md-1,
  .seven-cols .col-sm-1,
  .seven-cols .col-lg-1 {
    width: 14.285714285714285714285714285714%;
  }
}

cols.html

<div class="container">
  <div class="row seven-cols">
    <div class="col-md-1">Col 1</div>
    <div class="col-md-1">Col 2</div>
    <div class="col-md-1">Col 3</div>
    <div class="col-md-1">Col 4</div>
    <div class="col-md-1">Col 5</div>
    <div class="col-md-1">Col 6</div>
    <div class="col-md-1">Col 7</div>
  </div>
</div>

Thanks for Bootstrap 4 update!