Size Converter & Aspect Ratio Calculator

✓ Free Online Aspect Ratio & Size Calculator

Lock the aspect ratio, resize to any target box, and convert px, cm, mm, in and pt with DPI — instantly, right in your browser.

🔒 Ratio lock — Type a new width and the height follows the original aspect ratio automatically — or unlock for free editing.
🎯 Target size modes — Fit width, fit height, or go free-form with a live distortion warning showing exactly how much the image stretches.
🖼️ Contain / cover / stretch — Give a container size and see all three fit results at once, with scale factor plus letterbox or crop pixels.
📐 Units and DPI — Convert between px, cm, mm, inch and pt at 72, 96, 150, 300, 350 DPI or any custom value.

Full guide, how-to & FAQ →

⚠️ JavaScript is required This tool runs entirely in your browser and needs JavaScript. Please enable JavaScript, or open this page in a modern browser with JavaScript support, to use all features.

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