Vertically centering text inside flexbox item

Question

I want the flex items to take full height, but the content inside them to be vertically centred.

justify-content: centre doesn't work, and align-self: centre on the item itself shrinks its height to its own content, while I want all items to be the same height.

In this example I want the numbers to be vertically centred: http://codepen.io/ilyador/pen/ogYbWO?editors=110

.flex-container {
  padding: 0;
  margin: 0;
  list-style: none;
  display: flex;  
}

.flex-item {
  flex: 1 1;
  background: tomato;
  padding: 5px;
  margin-top: 10px;
  color: white;
  font-weight: bold;
  font-size: 3em;
  text-align: center;
  border: solid 1px red;
}

<ul class="flex-container">
  <li class="flex-item">1fbdms s s sdj dfkg kjfg dkfj gdfjkgdfkj gdfkjg dfkjgdkhdfjk gkjdfkjdfgdfg jkdfgdfjkgk </li>
  <li class="flex-item">2</li>
  <li class="flex-item">3</li>
  <li class="flex-item">4</li>
  <li class="flex-item">5</li>
  <li class="flex-item">6</li>
</ul>

Answer 1

I was able to accomplish vertical centering of your numbers with this:

.flex-item {
  display:flex;
  flex-direction:column;
  justify-content:space-around;
}

If you want something to be vertically centered, set the container to display:flex and then use justify-content to accomplish it. With justify-content you could either set it to space-around or to center. Either will accomplish your goal.

http://codepen.io/anon/pen/RNoajg

Answer 2

Give the flex items display: flex and align-items: center. The flex items contents will now be vertically centered.

body {
  display: flex;
  height: 100vh;
  margin: 0;
}
body > div {
  flex: 1;
  display: flex;
  align-items: center;
  background: #F00;
}
body > div:nth-child(odd) {
  background: #F90;
}

<div>
  <p>This</p>
</div>
<div>
  <p>text</p>
</div>
<div>
  <p>is</p>
</div>
<div>
  <p>vertically</p>
</div>
<div>
  <p>centered</p>
</div>