bootstrap comes with clas btn-lg http://getbootstrap.com/components/#btn-dropdowns-sizing
<div class="btn btn-default btn-block">
Active
</div>
but if you want to have the button of the width of your column / container add btn-block
<div class="btn btn-default btn-lg">
Active
</div>
However this will expand to 100% so make surt ethat you will wrap your button in certain amount of columns e.g. then you know its always stays 3 columns until xs screen
<div class="col-sm-3">
<div class="btn btn-default btn-block">
Active
</div>
</div>