Why does grid-gap cause an overflow?
You have a 3-column grid container (.body
):
grid-template-columns: 25% 50% 25%
The total width of those columns is 100%.
You're then adding gutters between the columns (and rows):
grid-gap: 10px
which is shorthand for:
grid-column-gap: 10px;
grid-row-gap: 10px;
So when you add up all the widths you get:
25% + 50% + 25% + 10px + 10px
Put more briefly:
100% + 20px > 100%, which results in an overflow condition
(Note: grid-*-gap
properties apply only between grid items – never between items and the container. That's why we calculate two grid gaps, not four.)
As a solution, instead of percentage units, try using fr
units, which apply only to free space. This means that fr
lengths are calculated after any grid-gap
lengths are applied.
grid-template-columns: 1fr 2fr 1fr
div:not(.header):not(.body):not(.row) {
border: 1px solid grey;
}
.header {
margin-top: 20px;
display: grid;
grid-gap: 10px;
grid-template-areas: "header-left header-right-up" "header-left header-right-down";
grid-template-rows: 40px 40px;
grid-template-columns: minmax(50px, 200px) auto;
}
.header-left {
grid-area: header-left;
}
.header-right-up {
grid-area: header-right-up;
}
.header-right-down {
grid-area: header-right-down;
}
.body {
margin-top: 20px;
display: grid;
grid-template-columns: 1fr 2fr 1fr; /* ADJUSTMENT */
grid-auto-rows: 80px;
grid-gap: 10px;
}
.row-left {}
.row-center {}
.row-right {}
<div class="header">
<div class="header-left">image</div>
<div class="header-right-up">content</div>
<div class="header-right-down">long content</div>
</div>
<div class="body">
<div class="row-left"></div>
<div class="row-center"></div>
<div class="row-right"></div>
<div class="row-left"></div>
<div class="row-center"></div>
<div class="row-right"></div>
<div class="row-left"></div>
<div class="row-center"></div>
<div class="row-right"></div>
</div>
revised codepen demo
More details here: The difference between percentage and fr units in CSS Grid Layout
If you want to use percentages or some other unit, there is one more solution. The use of the minmax()
function will allow the columns to shrink to fit the parent container and not cause overflow.
The solution would look like this:
grid-template-columns: minmax(auto, 25%) minmax(auto, 50%) minmax(auto, 25%);
gap: 10px;
More on the minmax()
function here.