How can I change the default width of a Twitter Bootstrap modal box?

Answer 1

If you want something that does not break the relative design try this:

body .modal {
  width: 90%; /* desired relative width */
  left: 5%; /* (100%-width)/2 */
  /* place center */
  margin-left:auto;
  margin-right:auto; 
}

As, @Marco Johannesen says, the "body" before the selector is so that it takes a higher priority than the default.

Answer 2

Add the following on your css file

.popover{
         width:auto !important; 
         max-width:445px !important; 
         min-width:200px !important;
       }

Answer 3

In Bootstrap 3+ the most appropriate way to change the size of a modal dialog is to use the size property. Below is an example, notice the modal-sm along the modal-dialog class, indicating a small modal. It can contain the values sm for small, md for medium and lg for large.

<div class="modal fade" id="ww_vergeten" tabindex="-1" role="dialog" aria-labelledby="modal_title" aria-hidden="true">
  <div class="modal-dialog modal-sm"> <!-- property to determine size -->
    <div class="modal-content">
      <div class="modal-header">
        <button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button>
        <h4 class="modal-title" id="modal_title">Some modal</h4>
      </div>
      <div class="modal-body">

        <!-- modal content -->

      </div>
      <div class="modal-footer">
        <button type="button" class="btn btn-primary" id="some_button" data-loading-text="Loading...">Send</button>
      </div>
    </div>
  </div>
</div>

Answer 4

Use Below Script:

.modal {
  --widthOfModal: 98%;
  width: var(--widthOfModal) !important;
  margin-left: calc(calc(var(--widthOfModal) / 2) * (-1)) !important;
  height: 92%;

  overflow-y: scroll;
}

Demo:

Answer 5

I solved it for Bootstrap 4.1

Mix of previously posted solutions

.modal-lg {
  max-width: 90% !important; /* desired relative width */
  margin-left:auto !important;
  margin-right:auto !important;
}

Answer 6

Less-based solution (no js) for Bootstrap 2:

.modal-width(@modalWidth) {
    width: @modalWidth;
    margin-left: -@modalWidth/2;

    @media (max-width: @modalWidth) {
        position: fixed;
        top:   20px;
        left:  20px;
        right: 20px;
        width: auto;
        margin: 0;
        &.fade  { top: -100px; }
        &.fade.in { top: 20px; }
    }
}

Then wherever you want to specify a modal width:

#myModal {
    .modal-width(700px);
}