Aspect Ratio Calculator — Find Width, Height & Ratio

The 16:9 ratio is the dominant standard for modern video and digital displays — HD (1280×720), Full HD (1920×1080), 4K (3840×2160), and most monitor and TV screens use this ratio. The 4:3 ratio was the standard for analogue television and older computer monitors; it remains common in document scanning and some tablet orientations. The 1:1 (square) ratio is widely used for social media profile images and Instagram posts. The 21:9 (ultrawide) ratio is used for cinematic content and gaming monitors. The 9:16 ratio is the vertical equivalent of 16:9, used for smartphone screens, TikTok, Instagram Stories, and YouTube Shorts. The 3:2 ratio appears in 35mm film photography and many DSLR cameras, as well as Microsoft Surface tablets.

When you enter dimensions like 1920×1080, the calculator finds the Greatest Common Divisor (GCD) — the largest integer that divides both numbers evenly. For 1920 and 1080, the GCD is 120. Dividing both by 120 gives 16:9. This simplification reveals the underlying proportional relationship. For 1280×720, the GCD is 80, and 1280÷80 : 720÷80 = 16:9 — confirming both are the same ratio. Note that some dimensions produce unusual ratios: 2560×1080 simplifies to 64:27 rather than the expected 21:9 (which would be 2520×1080). When comparing ratios across different resolutions, it is more accurate to compare the decimal equivalent (width ÷ height): 16:9 ≈ 1.777, 4:3 ≈ 1.333, 21:9 ≈ 2.333.

Video production requires strict adherence to aspect ratios to avoid letterboxing (black bars on top and bottom), pillarboxing (black bars on sides), or distortion. YouTube accepts 16:9 as the standard; uploading a 4:3 video results in pillarboxing. Social media platforms have different requirements: Instagram feed posts accept 4:5 (portrait) for maximum screen real estate, while Stories and Reels use 9:16. Twitter/X supports 16:9, 1:1, and 4:3 in video posts. When exporting from video editing software, always set the sequence preset to match your delivery format's aspect ratio before editing, not after — repositioning footage to fit a different ratio late in production is costly. For digital cinema, the DCI standard uses 1.85:1 (flat) or 2.39:1 (scope).

In web development, maintaining aspect ratios when resizing images is critical for layout consistency. If you have a hero image at 1440×810 (which is 16:9) and need a version that is 768 pixels wide, use the "Find Height" mode: enter width 768 and ratio 16:9 to get height 432. The CSS aspect-ratio property (aspect-ratio: 16 / 9) lets you define this in stylesheets without JavaScript. For img elements, setting only width or height (not both) in HTML causes the browser to maintain the natural aspect ratio automatically. When setting explicit dimensions in CSS, always use this calculator to ensure your specified height matches the image's native ratio — mismatched dimensions cause image distortion.

Photography and print work often requires cropping images to specific aspect ratios. A standard 4×6 inch print corresponds to a 3:2 ratio (6÷4 = 1.5, and 3:2 = 1.5). An 8×10 print is 4:5, which means a 3:2 photo needs to be cropped or padded. For digital photos from a 24MP camera (6000×4000 pixels), the aspect ratio is 3:2. Cropping to 16:9 for a widescreen presentation at 6000 wide means the height should be 6000 ÷ (16/9) = 3375 pixels — use this calculator's "Find Height" mode to verify. Photo editing software allows non-destructive cropping, so always check the target ratio before cropping to ensure you do not inadvertently remove important parts of the composition.