Bootstrap 3 modal vertical position center

Question

This is a two part question:

1. How can you position the modal vertically in the center when you don\'t know the exact height of the modal?

2. Is

Answer 1

All what I did in my case is to set the Top in my css knowing the height of the modal

...

in my css i set

#myModal{
    height: 400px;
    top: calc(50% - 200px) !important;
}