How margin: 0 auto; centers the element?

#css #html

Hi Everyone,

This is my first post in dev.to 😀
Here, we are going to talk about how margin: 0 auto; works

let's consider the div(.inner-div) element inside another div(.outer-div) element

HTML:
<div class="outer-div">
<div class="inner-div"></div>
</div>

CSS:
.outer-div {
width: 100px;
height: 100px;
background-color: red;
}

.inner-div {
width: 50px;
height: 100px;
background-color: blue;
margin: 0 auto;
}

Output:

Actually the inner-div has an auto value for both margin-left and margin-right properties.

These auto values align the inner-div in the center position of outer-div.
Because the inner-div exactly has a 25px on margin-left and 25px on margin-right.

Why 25px? 🤔
The outer div has a 100px width. The Inner-div has a 50px width;
Remaining width(total margin values of left and right) = 100 - 50 = 50px;

marginLeft = marginRight = 50/2 = 25px;
So, We conclude the formula as 😜

Total margin values of left and right = parent element width - child 
                                        element width
  marinLeft = marginRight = Total margin values of left and right/2

Therefore, .inner-div is centered.

Note: margin: 10px auto: also centers the element, but it will take 10px on top as well as the bottom. So, the left and right auto values will
make the center position.