Image Resizer — Pixels, Percentage & Target KB

How to resize an image without losing quality

Image quality loss during resizing comes from pixel interpolation — the process of calculating new pixel values when changing dimensions. Downscaling (making images smaller) preserves quality well because the algorithm has more data than it needs and simply averages nearby pixels. Upscaling (making images larger) always reduces quality because the tool must invent pixel data that doesn't exist, producing blurry or pixelated results.

Resizing and compression are different operations that often work together. Resizing changes pixel dimensions (width and height), while compression changes file size by removing or approximating image data. For the smallest possible file, resize to the maximum display size first, then compress. Serving a 4000px image in a 400px container wastes bandwidth — resize to what you actually need.

The “resize to KB” use case is one of the most common: email attachment limits, profile picture uploads, and web form restrictions all impose file size constraints. This tool's Target File Size mode handles this by iteratively adjusting both dimensions and compression quality until your target is reached.

Image size guide for every social media platform (2025)

Social media platforms specify recommended image dimensions to prevent quality loss from re-compression and display cropping. When you upload an image that doesn't match the expected aspect ratio, platforms crop it — often cutting off important content. Oversized images get re-compressed by the platform, adding artefacts. Uploading at the exact recommended dimensions gives you the best visual quality.

Key dimensions: Instagram feed posts use 1080×1080px (square), 1080×1350px (portrait), or 1080×566px (landscape). Facebook feed images are 1200×630px. Twitter/X post images are 1600×900px. LinkedIn post images are 1200×627px. YouTube thumbnails are 1280×720px. Pinterest standard pins are 1000×1500px. Use the social media presets panel above to set these dimensions with one click. Note that platforms occasionally update these specs — verify with each platform's official documentation for the most current requirements.