Using margin on flex items

Question

I was under the impression that a margin can be added to flex items/children, and flexbox should automatically take that into account and calculate the correct spacing between the items.

I can't seem to get this working as I would like though.

Fiddle here: https://jsfiddle.net/dba5ehcw/1/

.flex-item{
    border: 1px solid blue;
    box-sizing: border-box;
    height: 160px;
    width: 50%;
}

So each flex item at the moment is half the width of the container, and they flow nicely next to each other.

I would like to be able to add a margin of say, 1em to the flex-items in order to give them some breathing room, but in doing so, they become larger than the 50% and no longer stack next to each other on the same line because they are too wide.

Is there a way to use margin on the flex-items and have the flexbox container take this into account and adjust (decrease) their widths accordingly?

Answer 1

You need to do it with padding - which, when in border-box mode does not make the container larger than its specified width - not margin, and a nested flex div. This is how all flexbox-based grid systems work. Code below:

.flex-container{
    border: 1px solid red;
    box-sizing: border-box;
    display: flex;
    flex-wrap: wrap;
    width: 320px;
}

.flex-item{
    padding:1em;
    box-sizing: border-box;
    height: 160px;
    width: 50%;
    display:flex;
}

.flex-item>div {
    border: 1px solid blue;
    flex: 1 1 auto;
}

<div class="flex-container">
    <div class="flex-item"><div></div></div>
    <div class="flex-item"><div></div></div>
    <div class="flex-item"><div></div></div>
    <div class="flex-item"><div></div></div>
    <div class="flex-item"><div></div></div>
    <div class="flex-item"><div></div></div>
</div>