Aspect Ratio Calculator
Simplify an image or video aspect ratio, or find a missing width or height — free, instant, no upload needed.
About This Tool
The TulQR Aspect Ratio Calculator does two things: it simplifies any width-and-height pair down to its lowest-terms ratio using the Euclidean GCD algorithm, and it solves for a missing width or height when you already know the target ratio and one dimension. Everything updates instantly as you type — no upload, no sign-up, and nothing leaves your browser.
Why Aspect Ratio Matters
Aspect ratio is the proportional relationship between an image or video's width and height, and getting it right avoids stretching, black bars, or awkward cropping. For video, export presets like 16:9 (standard YouTube and widescreen playback), 9:16 (YouTube Shorts, TikTok, Instagram Reels), and 21:9 (cinematic widescreen) each require specific pixel dimensions — this calculator instantly tells you the exact height for a target width, e.g. 1920×1080 for 16:9 at Full HD.
For social media, platforms enforce different ratios: Instagram feed posts use 1:1 (square) or 4:5 (portrait), Instagram and Facebook Stories use 9:16, and Twitter/X link cards typically use 16:9 or 2:1. Uploading the wrong ratio means the platform crops or letterboxes your content automatically, often cutting off important parts of the image.
In print photography, common frame and paper sizes correspond to specific ratios — a 4×6 print is 3:2 (matching most DSLR and phone camera sensors), a 5×7 print is closer to 5:7, and an 8×10 print is 4:5. Knowing the underlying ratio helps you crop a photo before ordering prints so nothing important gets trimmed off the edges.
In UI and product design, aspect ratio governs everything from monitor resolutions (16:9 and 21:9 ultrawide are now standard) to card components, thumbnails, and hero banners in a design system. Designers often lock a container to a fixed ratio — 16:9 video embeds or 1:1 avatar thumbnails — so layouts stay consistent regardless of the source image's original dimensions.
Whether you're exporting a video for YouTube, sizing an Instagram carousel, ordering prints, or setting up a responsive image container in CSS, this calculator removes the guesswork — simplify a ratio to check it against a known standard, or plug in a target ratio and one dimension to get the exact matching size.
Frequently Asked Questions
How is the ratio simplified?
The calculator finds the greatest common divisor (GCD) of the width and height using the Euclidean algorithm, then divides both numbers by it. For example, 1920×1080 reduces to 16:9 because their GCD is 120.
Can I find a missing width or height?
Yes — switch to "Find a Missing Dimension," enter your target ratio (e.g. 16:9), choose whether you're providing the width or height, and the other value is calculated instantly.
What do the decimal ratio numbers mean?
The decimal ratio is width divided by height. 16:9 is approximately 1.778, 4:3 is approximately 1.333, and 1:1 (square) is exactly 1.000. It's a quick way to compare ratios that aren't in simple whole-number form.
Does it work for non-integer dimensions?
Yes, though GCD simplification rounds to the nearest whole pixel first since most real-world width and height values — images, video, screens — are integers.
Which ratio should I use for YouTube or TikTok?
YouTube videos are typically exported at 16:9. YouTube Shorts, TikTok, and Instagram Reels use the vertical 9:16 ratio. Instagram feed posts commonly use 1:1 or 4:5.