Why margin on child element moves the parent element in CSS ?

Last Updated : 26 Apr, 2023

In CSS, when a margin is applied to a child element, it can affect the position of the parent element. This happens because the margins of an element collapse with the margins of its adjacent siblings or its parent, based on certain rules. If the parent element has no padding or border, and the child element has a top margin, then the child element’s margin collapses with the parent element’s margin, causing the parent element to move along with the child element.

In the below code, we have a parent div element with a blue background color, a child div element with a coral background color, and a 50-pixel top margin. When we run the HTML file in a browser and inspect the elements, we’ll see that the child element’s margin has pushed the parent element down by 50 pixels, causing it to appear lower on the page.

Example:

HTML

<!DOCTYPE html> 
<html lang="en"> 
  
<head> 
    <meta charset="UTF-8" /> 
    <meta http-equiv="X-UA-Compatible" content="IE=edge" /> 
    <meta name="viewport" content= 
        "width=device-width, initial-scale=1.0" /> 
  
    <style> 
        .parent { 
            background-color: lightblue; 
            width: 300px; 
        } 
  
        .child { 
            background-color: lightcoral; 
            width: 150px; 
            margin-top: 50px; 
        } 
    </style> 
</head> 
  
<body> 
    <div class="parent"> 
        <div class="child"> 
            I am a child element. 
        </div> 
    </div> 
</body> 
  
</html>

Output:

To solve the above problem, two common approaches can be used. Let’s see them one by one.

Approach 1: Add padding or border to the parent element

One way to prevent the child element’s margin from collapsing with the parent element’s margin is to add padding or a border to the parent element. This creates a “barrier” between the parent and child margins, preventing them from collapsing.

Syntax:

.parent {
    padding: 1px;
    /* or */
    border: 1px solid; 
}

Example: In the example, we added a 1px solid border to the parent element. This prevents the child element’s margin from collapsing with the parent element’s margin. As a result, the parent element stays in place, and the child element is positioned below it with a 50px margin.

HTML

<!DOCTYPE html> 
<html lang="en"> 
  
<head> 
    <meta charset="UTF-8" /> 
    <meta http-equiv="X-UA-Compatible" content="IE=edge" /> 
    <meta name="viewport" content= 
        "width=device-width, initial-scale=1.0" /> 
  
    <style> 
        .parent { 
            background-color: lightblue; 
            width: 300px; 
            border: 1px solid; 
        } 
  
        .child { 
            background-color: lightcoral; 
            width: 150px; 
            margin-top: 50px; 
        } 
    </style> 
</head> 
  
<body> 
    <div class="parent"> 
        <div class="child"> 
            I am a child element. 
        </div> 
    </div> 
</body> 
  
</html>

Output:

Approach 2: Using Overflow Property on Parent Element

Another way to prevent the parent element from moving due to a child element’s margin is to use the overflow property on the parent element. By setting the overflow property to “auto” or “hidden” we can create a new block formatting context for the parent element, which prevents its margin from collapsing with the child element’s margin.

Syntax:

.parent {
       overflow: auto;
       /* or */
       overflow: hidden;
}

Example: In this example, we set the overflow property of the parent element to “auto”, which creates a new block formatting context for the parent element. This prevents the margin of the child element from collapsing with the margin of the parent element. As a result, the parent element stays in place, and the child element is positioned below it with a 50px margin.

HTML

<!DOCTYPE html> 
<html lang="en"> 
  
<head> 
    <meta charset="UTF-8" /> 
    <meta http-equiv="X-UA-Compatible" content="IE=edge" /> 
    <meta name="viewport" content= 
        "width=device-width, initial-scale=1.0" /> 
  
    <style> 
        .parent { 
            background-color: lightblue; 
            width: 300px; 
            overflow: auto; 
        } 
  
        .child { 
            background-color: lightcoral; 
            width: 150px; 
            margin-top: 50px; 
        } 
    </style> 
</head> 
  
<body> 
    <div class="parent"> 
        <div class="child"> 
            I am a child element. 
        </div> 
    </div> 
</body> 
  
</html>