How to set the height of an button (input-element) on webkit browsers?

Button is an inline-level element. You need to change that to block or inline-block:

#my_button { display: inline-block; height: 200px; }

Live Example

Display inline-block does nothing, as inputs already have that display set by default. Add border:none. When you do so, it starts behaving like you want it to. Here's the fiddle -> http://jsfiddle.net/joplomacedo/XmS6m/1/

Try setting the box-sizing property to content-box:

.my-button {
  box-sizing: content-box;
  height: 200px;
}