Aspect Ratio Calculator — Calculate, Scale, and Compare
Our free aspect ratio calculator helps you find the aspect ratio of any dimensions, scale images and videos to new sizes while preserving the ratio, and compare two ratios side by side. Includes presets for all major social media platforms, video standards, and print formats.
What Is Aspect Ratio?
Aspect ratio is the proportional relationship between the width and height of an image, screen, or frame. It is expressed as two numbers separated by a colon — for example 16:9 means the width is 16 units for every 9 units of height. Aspect ratio describes shape, not size: a 1920×1080 monitor and a 1280×720 monitor both have a 16:9 aspect ratio even though they are different sizes.
Understanding aspect ratio is essential in photography, videography, web design, social media content creation, and print design. The wrong aspect ratio causes images to appear stretched, cropped, or letterboxed with black bars.
How to Calculate Aspect Ratio
To find the aspect ratio of any dimensions, divide both width and height by their greatest common divisor (GCD):
Step 1: Find the GCD of width and height. For 1920 and 1080, the GCD is 120.
Step 2: Divide both by the GCD. 1920 ÷ 120 = 16. 1080 ÷ 120 = 9.
Result: 16:9.
Common Aspect Ratios Reference
| Ratio | Decimal | Common Name | Typical Use |
|---|---|---|---|
| 1:1 | 1.000 | Square | Instagram posts, profile photos |
| 4:3 | 1.333 | Standard / Traditional | Old TV, iPad, some cameras |
| 3:2 | 1.500 | Standard Camera | 35mm film, DSLR, mirrorless cameras |
| 16:10 | 1.600 | Widescreen | MacBook displays, older monitors |
| 16:9 | 1.778 | Widescreen HD | HD/4K video, YouTube, most monitors |
| 1.85:1 | 1.850 | Academy Flat | Cinematic film (US standard) |
| 2:1 | 2.000 | Univisium | Some streaming content |
| 2.39:1 | 2.390 | CinemaScope | Widescreen cinema, anamorphic |
| 21:9 | 2.333 | Ultrawide | Gaming monitors, some phones |
| 32:9 | 3.556 | Super Ultrawide | Samsung super ultrawide monitors |
| 9:16 | 0.563 | Vertical / Portrait | Smartphone video, Stories, Reels |
| 4:5 | 0.800 | Portrait | Instagram portrait posts |
Aspect Ratios for Social Media
Each social media platform has its own recommended aspect ratios. Using the correct ratio prevents automatic cropping that cuts off important parts of your image or video.
| Platform | Content Type | Ratio | Recommended Size | Notes |
|---|---|---|---|---|
| Square Post | 1:1 | 1080×1080 | Safe for all feeds | |
| Portrait Post | 4:5 | 1080×1350 | Takes more feed space | |
| Story / Reel | 9:16 | 1080×1920 | Full screen vertical | |
| Landscape Post | 1.91:1 | 1080×566 | Wide format | |
| Twitter/X | Post image | 16:9 | 1200×675 | Recommended |
| Twitter/X | Profile header | 3:1 | 1500×500 | Cover photo |
| Post image | 1.91:1 | 1200×630 | Link preview | |
| Story | 9:16 | 1080×1920 | Full screen | |
| Post image | 1.91:1 | 1200×627 | Feed post | |
| YouTube | Video | 16:9 | 1920×1080 | Standard HD |
| YouTube | Thumbnail | 16:9 | 1280×720 | Click-through |
| TikTok | Video | 9:16 | 1080×1920 | Full screen vertical |
Aspect Ratios for Video Production
| Standard | Ratio | Resolution | Use Case |
|---|---|---|---|
| SD (Standard Definition) | 4:3 | 640×480 | Legacy video |
| HD (720p) | 16:9 | 1280×720 | Basic web video |
| Full HD (1080p) | 16:9 | 1920×1080 | Standard broadcast |
| QHD (1440p) | 16:9 | 2560×1440 | High quality streaming |
| 4K UHD | 16:9 | 3840×2160 | Premium streaming, cinema |
| 4K DCI Cinema | 1.9:1 | 4096×2160 | Digital cinema |
| 8K UHD | 16:9 | 7680×4320 | Future standard |
| Anamorphic Cinema | 2.39:1 | Variable | Widescreen film look |
| Vertical Video | 9:16 | 1080×1920 | Mobile-first content |
How to Resize Images Without Distortion
When resizing an image, always scale both dimensions by the same factor to preserve the aspect ratio. Changing only one dimension stretches or squashes the image, making subjects look unnaturally wide or tall.
The safe resizing formula: if you know the new width, calculate the new height as: New Height = (New Width ÷ Original Width) × Original Height. If you know the new height, calculate the new width as: New Width = (New Height ÷ Original Height) × Original Width.
Use the Scale Dimensions mode of this calculator to handle this math automatically — enter your original dimensions and target size and the calculator does the rest.