How to make Flexbox Children 100% Height of their Parent using CSS? Last Updated : 11 Jul, 2025 Comments Improve Suggest changes Like Article Like Report Flexbox is an incredibly powerful layout model in CSS, enabling developers to create responsive designs with ease. It's especially effective—used in over 85% of modern websites—for distributing space evenly among child elements and aligning them efficiently. One common use case is when you want child elements to take up the full height (100%) of their parent container, ensuring a consistent and balanced layout regardless of screen size 1. Using Flexbox and the Height PropertyWe can use the display: flex property to create a flexbox child and use the height: 100% property to make the flex height 100% of the container. This method ensures that the child flexbox takes the full height of the parent container. index.html <!DOCTYPE html> <html> <head> <style> * { padding: 0; margin: 0; } .container { width: 100vw; height: 20vh; background-color: green; display: flex; justify-content: center; align-items: center; } .child-div { height: 100%; background-color: red; margin: 0 20px; } </style> </head> <body> <div class="container"> <div class="child-div"> One </div> <div class="child-div"> Two </div> <div class="child-div"> Three </div> <div class="child-div"> Four </div> <div class="child-div"> Five </div> </div> </body> </html> Output2. Using align-item PropertyThe align-items: stretch; approach ensures that flexbox children automatically stretch vertically to fill the entire height of their parent container, eliminating the need for explicit height declarations on the children. index.html <!DOCTYPE html> <html> <head> <style> * { padding: 0; margin: 0; } .container { width: 100vw; background-color: green; display: flex; justify-content: center; align-items: stretch; height: 30vh; } .child-div { background-color: red; margin: 0 20px; } </style> </head> <body> <div class="container"> <div class="child-div"> One </div> <div class="child-div"> Two </div> <div class="child-div"> Three </div> <div class="child-div"> Four </div> <div class="child-div"> Five </div> </div> </body> </html> OutputNote: CSS is the foundation of webpages and is used for webpage development by styling websites and web apps. You can learn CSS from the ground up by following this CSS Tutorial and CSS Examples. Comment More infoAdvertise with us Next Article CSS Introduction P Pankaj_Singh Follow Improve Article Tags : Web Technologies CSS CSS-Questions Similar Reads CSS Tutorial CSS stands for Cascading Style Sheets. It is a stylesheet language used to style and enhance website presentation. CSS is one of the three main components of a webpage, along with HTML and JavaScript.HTML adds Structure to a web page.JavaScript adds logic to it and CSS makes it visually appealing or 7 min read CSS Introduction CSS (Cascading Style Sheets) is a language designed to simplify the process of making web pages presentable.It allows you to apply styles to HTML documents by prescribing colors, fonts, spacing, and positioning.The main advantages are the separation of content (in HTML) and styling (in CSS) and the 4 min read CSS Syntax CSS is written as a rule set, which consists of a selector and a declaration block. The basic syntax of CSS is as follows:The selector is a targeted HTML element or elements to which we have to apply styling.The Declaration Block or " { } " is a block in which we write our CSS.HTML<html> <h 2 min read CSS Selectors CSS Selectors are used to target HTML elements on your pages, allowing you to apply styles based on their ID, class, type attributes, and more. There are mainly 5 types of selectors.Basic CSS Selectors: These are used to target elements by tag, .class, or # ID for fundamental styling needs.Combinato 7 min read CSS Comments CSS comments are used to add notes or explanations to your code, helping you and others understand it better. They start with /* and end with */ and can be used for both single-line and multi-line comments. Note: Comments are ignored by browsers, so they won’t affect how your webpage looks or works. 2 min read CSS Colors CSS colors are used to set the color of different parts of a webpage, like text, background, and borders. 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Their values can be set using length, percentage, or auto.Width and HeightThe width and height properties in CSS are used to define the dimensions of an element. The values can be set in various units, such as pixels (px), centim 4 min read CSS Outline CSS outline is a property used to draw a line around an element's border. It does not affect the layout, unlike borders. It's often used to highlight elements, providing a visual emphasis without altering the dimensions of the element.Syntaxselector{ outline: outline-width outline-type outline-color 4 min read Like