Bootstrap change carousel height

like Answers above, if you do bootstrap 4 just add few line of css to .carousel , carousel-inner ,carousel-item and img as follows

.carousel .carousel-inner{
height:500px
}
.carousel-inner .carousel-item img{
min-height:200px;
//prevent it from stretch in screen size < than 768px
object-fit:cover
}

@media(max-width:768px){
.carousel .carousel-inner{
//prevent it from adding a white space between carousel and container elements
height:auto
 }
}

You may also want to add

object-fit: cover;

To preserve the aspect ration for different window sizes

.carousel .item {
  height: 500px;
}

.item img {
    position: absolute;
    object-fit:cover;
    top: 0;
    left: 0;
    min-height: 500px;
}

For Bootstrap 4 and above replace .item with .carousel-item

.carousel .carousel-item {
  height: 500px;
}

.carousel-item img {
    position: absolute;
    object-fit: cover;
    top: 0;
    left: 0;
    min-height: 500px;
}

From Bootstrap 4

.carousel-item{
    height: 200px;
} 
.carousel-item img{
    height: 200px;
}

The following should work

.carousel .item {
  height: 300px;
}

.item img {
    position: absolute;
    top: 0;
    left: 0;
    min-height: 300px;
}

JSFiddle for reference.