Calculate width based on total width

#content {
  width: -moz-calc(100% - 10px);
  width: -webkit-calc(100% - 10px);
  width: -o-calc(100% - 10px);
  width: calc(100% - 10px);
}

Width only as wide as needed for the text

.My-Button {
  min-width: 86px;
  display: inline-block;
}