====== CSS - Height - DIV 100% height with padding/margin ======

If the parent element is 200px tall and the height is specify as 100% with padding 5px, it would be expected to get a 190px high element with border = 5px on all sides, nicely centered in the parent element.

The obvious answer does not work:

<code css>
#myDiv {
  width: 100%
  height: 100%;
  padding: 5px;
}
</code>

----

===== Solution =====

**display:block** is the default display value for a div, but **display:explicit** is also good.

The container has to be the right type; position attribute is fixed, relative, or absolute.

<code css>
.stretchedToMargin {
  display: block;
  position:absolute;
  height:auto;
  bottom:0;
  top:0;
  left:0;
  right:0;
  margin-top:20px;
  margin-bottom:20px;
  margin-right:80px;
  margin-left:80px;
  background-color: green;
}
</code>

<code html>
<div class="stretchedToMargin">
  Hello, world
</div>
</code>

----

Can also do percentage:

<code css>
*.stretchedMargin {
    display: block;
    position:absolute;
    height:auto;
    bottom:0;
    top:0;
    left:0;
    right:0;
    margin-top:1%;
    margin-right:50%;
    margin-left:5%;
    background-color: green;
}
</code>

----

<WRAP info>
**NOTE:**  This may not work with some older versions of i.e.

See the following to fix this:

https://code.google.com/archive/p/ie7-js/

</WRAP>

----

===== Using CSS box-sizing =====

There is a new property in CSS3 that you can use to change the way the box model calculates width/height, it's called box-sizing.

By setting this property with the value **border-box** it makes whichever element you apply it to not stretch when you add a padding or border.

If you define something with 100px width, and 10px padding, it will still be 100px wide.

<code css>
box-sizing: border-box;
</code>

See:  http://caniuse.com/#feat=css3-boxsizing

----

===== Using basic CSS =====

The solution is to NOT use height and width at all! Attach the inner box using top, left, right, bottom and then add margin.

<code css>
.box {
  margin:8px;
  position:absolute;
  top:0;
  left:0;
  right:0;
  bottom:0}
</code>

<code html>
<div class="box" style="background:black">
  <div class="box" style="background:green">
    <div class="box" style="background:lightblue">
      This will show three nested boxes. Try resizing browser to see they remain nested properly.
    </div>
  </div>
</div>
</code>


----

===== Using Calc =====

<code css>
#myDiv {
  width: calc(100% - 5px);
  height: calc(100% - 5px);
  padding: 5px;
}
</code>

<WRAP info>
**NOTE:**  Do not forget the space between the values and the operator (e.g. (100%-5px) that will break the syntax.
</WRAP>

See:  https://caniuse.com/#feat=calc

----