Aspect Ratio Calculator

The Aspect Ratio Calculator finds the proportional relationship between width and height of any rectangle and scales dimensions proportionally to a target size without distortion. Essential for video production, responsive web design, photography cropping, social media content creation and screen resolution comparison. Enter any two of three values — width, height and ratio — and the calculator instantly derives the missing dimension.

Common aspect ratios in digital media: 16:9 (YouTube, widescreen TV, PC monitors, standard landscape video), 9:16 (TikTok, Instagram Stories, YouTube Shorts), 4:3 (legacy TV, older iPads), 1:1 (Instagram square posts, profile pictures), 3:2 (DSLR cameras, 35mm film) and 21:9 (ultrawide monitors, cinematic films). Uploading a 16:9 video to a 9:16 platform results in letterboxing or aggressive cropping — both significantly reduce engagement. Planning the correct ratio before filming avoids costly reshoots.

For responsive web design, CSS preserves aspect ratios using the padding-bottom technique: set padding-bottom as (height divided by width) times 100 percent. A 16:9 container uses padding-bottom of 56.25 percent. Modern CSS provides the aspect-ratio property as a simpler alternative. After calculating dimensions, optimise images with our Image Compressor or calculate space requirements with our Room Area Calculator. Free, no registration required.