Calculate new dimensions while keeping the same aspect ratio. Perfect for resizing images, video, and design work.
Aspect ratio is the proportional relationship between an image or screen's width and height, expressed as two numbers separated by a colon (for example, 16:9 or 4:3). It defines the shape of the frame, not its size. A 16:9 ratio means for every 16 units of width, there are 9 units of height. This ratio is the same whether the screen is 32 inches wide and 18 inches tall, or 1920 pixels wide and 1080 pixels tall. Maintaining the correct aspect ratio when resizing prevents images and videos from appearing stretched or squished.
Enter any two of the three values: original width, original height, and the new width or new height you want. The calculator determines the missing dimension that preserves the original aspect ratio. It also displays the simplified ratio (for example, 1920x1080 simplifies to 16:9). You can use pixels, inches, centimeters, or any consistent unit.
16:9 is the standard for modern widescreen displays, YouTube videos, and most TV content. 4:3 is the classic TV and old monitor format, now common for iPads and some presentations. 1:1 is a square, standard for Instagram posts and profile pictures. 9:16 is vertical video for TikTok, Instagram Reels, and YouTube Shorts. 21:9 is ultrawide, used in cinema and ultrawide monitors. 3:2 is common in photography (DSLR sensors) and some laptops like the Surface line.
Aspect ratio is critical in several contexts. Social media: Each platform has preferred dimensions. Instagram posts are 1:1 or 4:5, Stories are 9:16, and feed videos are 1:1 or 16:9. Posting the wrong ratio results in cropping. Video editing: Mixing footage shot at different ratios requires letterboxing or cropping. Web design: Responsive images need to maintain their ratio at different viewport sizes to avoid distortion. Printing: A photo shot at 3:2 does not fit perfectly into a 4x6, 5x7, or 8x10 frame without cropping, because these frames have different aspect ratios.
Aspect ratio describes the proportional relationship between width and height. The most common ratios are: 16:9 (standard widescreen for HD and 4K television, YouTube, and most modern monitors), 4:3 (classic television and early computer monitors), 21:9 (ultrawide monitors and cinematic widescreen), 1:1 (Instagram square posts), 9:16 (vertical video for TikTok, Reels, and Stories), and 3:2 (most DSLR cameras and some laptops including Microsoft Surface). Cinema uses even wider ratios: 2.35:1 and 2.39:1 (anamorphic widescreen used in most Hollywood films).
When resizing images or video, maintaining the original aspect ratio prevents distortion. If you know one dimension and the aspect ratio, the other dimension is calculated automatically: for a 16:9 video that must be 1920 pixels wide, the height is 1920 x (9/16) = 1080 pixels. This is the standard 1080p HD resolution. Common resolution/aspect ratio pairs: 1920x1080 (16:9), 2560x1440 (16:9), 3840x2160 (16:9, "4K"), 1080x1080 (1:1), 1080x1920 (9:16).
Platform requirements dictate aspect ratio choices for content creators. YouTube prefers 16:9 (with 1920x1080 or 3840x2160 recommended). Instagram feed posts work best at 1:1 or 4:5 (portrait). Instagram Stories and TikTok require 9:16. Twitter/X displays 16:9 in-feed without cropping. LinkedIn posts display at 1.91:1. Designing for the wrong ratio results in awkward cropping, black bars, or stretched content. The QR Code Generator creates 1:1 square codes, and photography tools often need to crop to specific ratios for print sizes (8x10 is 4:5, 4x6 is 2:3).