When to Use Different Flex Size Units

Introduction

Flexbox is a powerful layout module that has become increasingly popular in web design. It allows you to create responsive layouts that adapt to different screen sizes quickly. One of the critical features of Flexbox is its ability to control the size of flex items. There are three central flex size units that you can use: auto, percentage (%), and pixels (px).

Auto

The auto unit is the default unit for flex items. It causes the flex item to grow or shrink to fit the content inside it. This is a good choice for text blocks and other elements that must be flexible in size.

Percentage (%)

The percentage unit defines the percentage of the container that the flex item will occupy. This is a good choice for elements that must maintain a consistent relative size across different screen sizes. For example, you might set two columns to each be 50% wide so they always take up half of the available space.

Pixels (px)

The pixels unit defines the size of the flex item in pixels. This is a good choice for elements that need to have a fixed size, such as images or buttons.

Here is a table summarising when to use each flex size unit:

Examples

Here are some examples of when to use each flex size unit:

• Text block: Use the auto unit to ensure the text block height grows or shrinks according to the amount of text inside it.

• Column width: Use the percentage unit to set two columns to each be 50% wide so they always take up half of the available space.

• Image: Use the pixels unit to set the width and height of an image to a fixed size, such as 200px by 200px.

Conclusion

By understanding when to use each flex size unit, you can create responsive layouts that adapt to different screen sizes and look great on any device.