$('.jcarousel').on('jcarousel:create jcarousel:reload', function() {
    var element = $(this),
        width = element.innerWidth();
        alert(width);

    // This shows 1 item at a time.
    // Divide `width` to the number of items you want to display,
    // eg. `width = width / 3` to display 3 items at a time.
    element.jcarousel('items').css('width', width + 'px');
}).jcarousel({
});

$('.jcarousel-control-prev').jcarouselControl({
    target: '-=1'
});

$('.jcarousel-control-next').jcarouselControl({
    target: '+=1'
});

/** Carousel **/

.jcarousel {
    position: relative;
    overflow: hidden;
    width: 100%;
}

.jcarousel ul {
    width: 20000em;
    position: relative;
    list-style: none;
    margin: 0;
    padding: 0;
 }

 .jcarousel li {
    width: 800px;
    float: left;
    border: 1px solid #fff;
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
    box-sizing: border-box;
}

.jcarousel img {
    display: block;
    max-width: 100%;
    height: auto !important;
}

<div class="jcarousel" data-jcarousel="true">