Aspect Ratio Calculator

Aspect ratio is the proportional relationship between the width and height of an image, video, or display. Expressed as two numbers separated by a colon (like 16:9 or 4:3), it describes the shape of your content rather than its actual size. For example, a 16:9 aspect ratio means for every 16 units of width, there are 9 units of height.

Our aspect ratio calculator helps you instantly determine ratios from pixel dimensions, calculate missing dimensions when you know the ratio, and resize images while maintaining their original proportions. Whether you're working with photographs, video content, or display resolutions, understanding aspect ratios prevents visual distortion and ensures your content looks professional across all platforms.

Using the correct aspect ratio is essential for creating visually appealing content. When images or videos are displayed in the wrong ratio, they appear stretched, squished, or cropped, ruining the intended visual experience. This is particularly important for photographers, videographers, graphic designers, and web developers.

Preventing Visual Distortion

Resizing an image without maintaining its original aspect ratio causes distortion. A portrait photo forced into a square frame will make faces appear wider or narrower than they should. Our calculator ensures you always resize proportionally, keeping the visual integrity of your content intact.

Social Media Platform Requirements

Each social media platform has specific aspect ratio requirements. YouTube videos use 16:9, Instagram posts prefer 1:1 (square) or 4:5 (portrait), TikTok and Reels require 9:16 (vertical), while Facebook cover photos need 2.7:1. Using the wrong ratio results in automatic cropping or black bars that diminish your content's impact.

Print and Photography

Standard print sizes follow specific aspect ratios. A 4×6 inch print has a 3:2 ratio, matching most DSLR camera sensors. However, an 8×10 inch print uses a 5:4 ratio, meaning photos must be cropped to fit. Understanding these differences helps photographers compose shots with the final print dimensions in mind.

16:9 – Widescreen Standard

The 16:9 aspect ratio is the universal standard for modern displays, HDTVs, computer monitors, and online video platforms like YouTube. Common resolutions include 1920×1080 (Full HD), 2560×1440 (QHD), and 3840×2160 (4K UHD). If you're creating video content for the web or television, 16:9 should be your default choice.

4:3 – Classic Fullscreen

The 4:3 ratio was the standard for older CRT televisions and computer monitors. While less common today, it's still used in iPad displays, presentation slides (PowerPoint defaults to 4:3), and retro-styled content. Standard resolutions include 1024×768 and 1600×1200.

21:9 – Ultrawide Cinema

Ultrawide monitors use the 21:9 aspect ratio, providing an immersive gaming and productivity experience. This ratio closely matches the 2.39:1 cinematic format used in Hollywood films, eliminating black bars when watching movies. Popular ultrawide resolutions include 2560×1080 and 3440×1440.

1:1 – Square Format

The 1:1 square aspect ratio gained popularity through Instagram's original photo format. It's ideal for profile pictures, social media posts, and album artwork. The equal width and height create balanced, symmetrical compositions that work well in grid-based layouts.

9:16 – Vertical Video

The inverse of 16:9, the 9:16 vertical ratio dominates mobile-first platforms like TikTok, Instagram Reels, YouTube Shorts, and Snapchat. As smartphone usage surpasses desktop, vertical video has become essential for reaching mobile audiences effectively.

While our aspect ratio calculator does the work instantly, understanding the math behind it helps you grasp the concept fully. To calculate aspect ratio from pixel dimensions, you need to find the greatest common divisor (GCD) of the width and height, then divide both values by it.

Example Calculation

For a 1920×1080 resolution: The GCD of 1920 and 1080 is 120. Dividing both: 1920÷120 = 16 and 1080÷120 = 9. Therefore, the aspect ratio is 16:9.

Finding Missing Dimensions

To find a missing dimension when you know the aspect ratio and one measurement, use cross-multiplication. For a 16:9 ratio with a width of 1280 pixels: Height = (1280 × 9) ÷ 16 = 720 pixels. This formula ensures your resized content maintains perfect proportions.

Decimal Aspect Ratios

Aspect ratios can also be expressed as decimal values. Simply divide width by height: 1920÷1080 = 1.778 (approximately 1.78:1). Decimal notation is commonly used in cinema, where formats like 2.39:1 (Cinemascope) and 1.85:1 (Academy Flat) are standard.

Choosing the right aspect ratio for video depends on your distribution platform and creative intent. Modern video editing software like Adobe Premiere Pro, Final Cut Pro, and DaVinci Resolve allows you to set custom sequence dimensions, but starting with the correct ratio saves time in post-production.

For YouTube and streaming platforms, always produce in 16:9 to avoid letterboxing. For cinema distribution, consider shooting in 2.39:1 or 1.85:1 depending on your film's aesthetic. When creating content for multiple platforms, shoot in the widest ratio and crop for vertical or square versions, ensuring important elements remain within the safe zone across all formats.

Frame rate and resolution work alongside aspect ratio to define your video's technical specifications. A 4K video at 16:9 equals 3840×2160 pixels, while the same 4K resolution at 21:9 ultrawide would be 5120×2160. Understanding these relationships ensures seamless delivery across devices and platforms.