Aspect Ratio Calculator
Resize dimensions while keeping the aspect ratio, with a visual preview
Change any field and the other side will be calculated automatically in proportion.
Instructions
Aspect Ratio Calculator Instructions\n\n## Overview\nWhen resizing images, videos or canvases, the biggest risk is distorting the ratio. This tool helps you keep the original ratio while converting the other side, and shows the simplified ratio.\n\n## How to Use\n1. Enter the original width and height (default 1920 × 1080)\n2. Change either the "new width" or "new height" field and the other is calculated automatically\n3. You can also click the common ratio buttons at the top (16:9, 4:3, 1:1, 21:9, 9:16, 3:2) to apply one quickly\n4. The results area shows the simplified ratio, decimal ratio, new dimensions and total pixel count, with a scaled diagram below\n\n## Notes\n- Decimal results are rounded to two decimal places; use whole pixels for actual exports\n- If the original ratio is unusual (for example 1920:1081), the simplified ratio is shown in decimal form instead\n- All calculations run in the browser; no images are uploaded
FAQ
Why calculate the ratio before resizing?
Stretching only the width or height distorts the image. Calculating the other side from the ratio keeps the image undistorted, which is exactly what the "keep aspect ratio" button does in image editing software.
What are common 16:9 sizes?
Common ones include 1920×1080, 1280×720, 2560×1440 and 3840×2160. Enter 1920 and 1080 as the original width and height, then set the new width to the value you want.
Which ratio is used for vertical videos?
The common vertical ratio for short videos is 9:16, for example 1080×1920 and 720×1280. Just click the 9:16 button to apply it.
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