WordPress automatically creates multiple image sizes when you upload a file, including a featured image. This plays a key role in how your content is displayed in archives, blog listings, and search previews. However, the size can vary dramatically depending on your theme and settings, which can lead to inconsistent layouts or performance issues.

This guide covers how to change the featured image size in WordPress manually and automatically. You’ll also learn best practices for featured image dimensions, common mistakes to avoid, and how image size affects performance and design.