How to set the iframe height & width to 100%

Question

I am in need of doing the following:

1. I have a header content which is 70px and an iframe with a wrapper. The height & width of the iframe has to be set to

Answer 1

I have a video frame in proportions 6:19 from YouTube -> by calculating 9/16 - 0.5625. multiplying with 95vw (you can also set to 100vW).

Worked the best to keep video ratio the same.

@media all and (max-width: 730px) {
    iframe{
        width: 95vw !important;
        height: calc(95vw*0.56) !important;
    }
}
    iframe{
    margin:auto;
    display:block;
    width:685px;
    height:385px;
}