How to make flexbox items the same size?

I want to use flexbox that has some number of items that are all the same width. I've noticed that flexbox distributes the space around evenly, rather than the space itself.

For example:

.header {
  display: flex;
}

.item {
  flex-grow: 1;
  text-align: center;
  border: 1px solid black;
}

<div class="header">
  <div class="item">asdfasdfasdfasdfasdfasdf</div>
  <div class="item">z</div>
</div>

The first item is a lot bigger than the second. If I have 3 items, 4 items, or n items, I want them all to appear on the same line with an equal amount of space per item.

Any ideas?

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

Set them so that their flex-basis is 0 (so all elements have the same starting point), and allow them to grow:

flex: 1 1 0px

Your IDE or linter might mention that the unit of measure 'px' is redundant. If you leave it out (like: flex: 1 1 0), IE will not render this correctly. So the px is required to support Internet Explorer, as mentioned in the comments by @fabb;

You could add flex-basis: 100% to achieve this.

Updated Example

.header {
  display: flex;
}

.item {
  flex-basis: 100%;
  text-align: center;
  border: 1px solid black;
}

For what it's worth, you could also use flex: 1 for the same results as well.

The shorthand of flex: 1 is the same as flex: 1 1 0, which is equivalent to:

.item {
  flex-grow: 1;
  flex-shrink: 1;
  flex-basis: 0;
  text-align: center;
  border: 1px solid black;
}

You need to add width: 0 to make columns equal if contents of the items make it grow bigger.

.item {
  flex: 1 1 0;
  width: 0;
}

Detail: flex: 1 1 0 is the same as flex-grow: 1; flex-shrink: 1; flex-basis: 0; and if the parent container can not provide enough space for the native-size added together of every item (no space to grow), we need to make the width: 0 to give every item the same start point to grow.

The accepted answer by Adam (flex: 1 1 0) works perfectly for flexbox containers whose width is either fixed, or determined by an ancestor. Situations where you want the children to fit the container.

However, you may have a situation where you want the container to fit the children, with the children equally sized based on the largest child. You can make a flexbox container fit its children by either:

• setting position: absolute and not setting width or right, or
• place it inside a wrapper with display: inline-block

For such flexbox containers, the accepted answer does NOT work, the children are not sized equally. I presume that this is a limitation of flexbox, since it behaves the same in Chrome, Firefox and Safari.

The solution is to use a grid instead of a flexbox.

When you run this snippet, make sure to click on full page to see the effect properly.

body {
  margin: 1em;
}

.wrap-inline-block {
  display: inline-block;
}

#div0, #div1, #div2, #div3, #div4 {
  border: 1px solid #888;
  padding: 0.5em;
  text-align: center;
  white-space: nowrap;
}

#div2, #div4 {
  position: absolute;
  left: 1em;
}

#div0>*, #div1>*, #div2>*, #div3>*, #div4>* {
  margin: 0.5em;
  color: white;
  background-color: navy;
  padding: 0.5em;
}

#div0, #div1, #div2 {
  display: flex;
}

#div0>*, #div1>*, #div2>* {
  flex: 1 1 0;
}

#div0 {
  margin-bottom: 1em;
}

#div2 {
  top: 15.5em;
}

#div3, #div4 {
  display: grid;
  grid-template-columns: repeat(3,1fr);
}

#div4 {
  top: 28.5em;
}

<p>Normal scenario — flexbox where the children adjust to fit the container — and the children are made equal size by setting {flex: 1 1 0}</p>

<div id="div0">
  <div>
    Flexbox
  </div>
  <div>
    Width determined by viewport
  </div>
  <div>
    All child elements are equal size with {flex: 1 1 0}
  </div>
</div>

<p>Now we want to have the container fit the children, but still have the children all equally sized, based on the largest child. We can see that {flex: 1 1 0} has no effect.</p>

<div class="wrap-inline-block">
<div id="div1">
  <div>
    Flexbox
  </div>
  <div>
    Inside inline-block
  </div>
  <div>
    We want all children to be the size of this text
  </div>
</div>
</div>

<div id="div2">
  <div>
    Flexbox
  </div>
  <div>
    Absolutely positioned
  </div>
  <div>
    We want all children to be the size of this text
  </div>
</div>

<br><br><br><br><br><br>
<p>So let's try a grid instead. Aha! That's what we want!</p>

<div class="wrap-inline-block">
<div id="div3">
  <div>
    Grid
  </div>
  <div>
    Inside inline-block
  </div>
  <div>
    We want all children to be the size of this text
  </div>
</div>
</div>

<div id="div4">
  <div>
    Grid
  </div>
  <div>
    Absolutely positioned
  </div>
  <div>
    We want all children to be the size of this text
  </div>
</div>

Im no expert with flex but I got there by setting the basis to 50% for the two items i was dealing with. Grow to 1 and shrink to 0.

Inline styling: flex: '1 0 50%',

None of these answers solved my problem, which was that the items weren't the same width in my makeshift flexbox table when it was shrunk to a width too small.

The solution for me was simply to put overflow: hidden; on the flex-grow: 1; cells.

None of these solutions worked for me, so I thought I'd share what did.

.header {
  display: flex;
}

.item {
  width: 100%;
}


/* Demo styles, for aesthetics. */

.demo {
  margin: 3rem;
}

.demo .item {
  text-align: center;
  padding: 3rem;
  background-color: #eee;
  margin: 0 1.5rem;
}

<div class="demo">
  <div class="header">
    <div class="item">
      1
    </div>
    <div class="item">
      2
    </div>
    <div class="item">
      3
    </div>
  </div>
</div>

<div class="demo">
  <div class="header">
    <div class="item">
      1
    </div>
    <div class="item">
      2
    </div>
  </div>
</div>

<div class="demo">
  <div class="header">
    <div class="item">
      1
    </div>
    <div class="item">
      2
    </div>
    <div class="item">
      3
    </div>
    <div class="item">
      4
    </div>
    <div class="item">
      5
    </div>
  </div>
</div>

This will work even if you wrapping items, like a Grid, but not so simple you should show where it will wrap in media queries))

example:

.flex-item{
     flex: 0 0 calc(25% - (45px / 4 ))
}

works like this:

$n: 4; // number of columns
$gap: 15px; // margin pixels

.flex-parent{
    display: flex;
    gap: $gap;
}
.flex-item{
     flex: 0 0 calc(100% / $n - (($n - 1) * $gap / $n ) );
}

on the child element of flex

flex: 1 1 25%

this will allow to have 4 items if you want to add more items then you can decrease the %