.iframe-wrap {
    position: relative;
    width: 100%;
    height: 0;
    padding-top: 60%;
}

@media screen and (max-width: 767px) {
    .iframe-wrap {
        padding-top: 75%;
    }
}

.iframe-wrap iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}