About This Tool
Calculate aspect ratios instantly with this free tool. Enter any width and height to get the simplified ratio, or pick a common preset like 16:9 or 4:3 and scale to your target resolution. Lock the ratio toggle keeps your proportions intact when you adjust one dimension. Need social media sizes? One-click presets load the exact pixel dimensions for Instagram, YouTube, TikTok, Twitter, Facebook, and LinkedIn. The tool also shows a live visual preview so you can see the shape of your ratio before exporting. Designers, video editors, and developers use aspect ratios daily when cropping photos, setting video export resolutions, building responsive layouts, and preparing assets for multiple platforms. Getting the ratio wrong leads to stretched or letterboxed content that looks unprofessional. This calculator removes the guesswork by doing the math for you. Your dimensions stay completely private and nothing is stored or shared.
How Aspect Ratios Work
An aspect ratio describes the proportional relationship between width and height. The ratio 16:9 means for every 16 units of width, there are 9 units of height. A 1920x1080 screen and a 3840x2160 screen both share the 16:9 ratio because dividing both dimensions by their greatest common divisor produces the same pair of numbers.
The calculation is straightforward: find the GCD (Greatest Common Divisor) of width and height using the Euclidean algorithm, then divide both dimensions by that number. For example, 1920 and 1080 share a GCD of 120, so 1920/120 = 16 and 1080/120 = 9, giving the ratio 16:9.
The decimal form of a ratio (width divided by height) is useful for quick comparisons. A 16:9 display has a decimal ratio of approximately 1.778, while a 4:3 display is approximately 1.333. A higher decimal ratio means a wider, more panoramic shape.
Common Aspect Ratios and Their Uses
- 16:9 is the standard for HD video, YouTube, and most computer monitors. It covers 1280x720, 1920x1080, and 3840x2160 resolutions.
- 4:3 was the classic TV and early computer monitor ratio. Still used in presentations, iPad screens, and some photography formats.
- 1:1 is a perfect square, common for Instagram posts, profile pictures, and album cover art.
- 9:16 is vertical video used by TikTok, Instagram Reels, YouTube Shorts, and Snapchat Stories.
- 21:9 is ultrawide, used in cinematic films and ultrawide gaming monitors.
- 3:2 is the standard for 35mm film and many DSLR cameras. Also used by Microsoft Surface devices.
Social Media Image Dimensions
Each social platform recommends specific pixel dimensions to avoid cropping or quality loss during upload:
- Instagram Post: 1080x1080 (1:1 square). Stories and Reels use 1080x1920 (9:16).
- YouTube Thumbnail: 1920x1080 (16:9). Minimum recommended is 1280x720.
- TikTok: 1080x1920 (9:16). Full-screen vertical format for maximum engagement.
- Twitter/X Post: 1200x675 (16:9). Timeline images are cropped to this ratio on desktop.
- Facebook Post: 1200x630 (roughly 1.9:1). Shared link previews follow this dimension.
- LinkedIn Post: 1200x627 (roughly 1.91:1). Similar to Facebook link previews.
Using the exact recommended dimensions ensures your images display without unintended cropping on each platform.
Scaling Dimensions Proportionally
When resizing an image, maintaining the aspect ratio prevents distortion. The math is simple: if you know the ratio (W:H) and one target dimension, solve for the other.
To find new height: new_height = target_width x (H / W)
To find new width: new_width = target_height x (W / H)
For example, to scale a 16:9 image to 1280px wide: height = 1280 x (9/16) = 720px. This tool handles all of that automatically when you enable ratio lock. Change the width and the height updates to maintain your locked proportion, or vice versa.
This is particularly useful for responsive web design where images must fit different screen sizes without stretching, and for video editing where output resolution must match the project aspect ratio.
Frequently Asked Questions
What is the aspect ratio of 1920x1080?
The aspect ratio of 1920x1080 is 16:9. This is the standard HD resolution used by most monitors, TVs, and video content. The greatest common divisor of 1920 and 1080 is 120, so dividing both by 120 gives 16 and 9.
How do I maintain aspect ratio when resizing an image?
Lock one dimension and calculate the other using the ratio. If your ratio is 16:9 and you set width to 800, the height should be 800 x (9/16) = 450. This tool does that calculation automatically when you enable the "Lock Aspect Ratio" toggle.
What aspect ratio should I use for YouTube videos?
YouTube recommends 16:9 for standard videos, which corresponds to resolutions like 1920x1080 (1080p) or 3840x2160 (4K). YouTube Shorts use 9:16 vertical format at 1080x1920. Uploading in the correct ratio avoids black bars or cropping.
What is the difference between 16:9 and 4:3?
16:9 is wider (widescreen) while 4:3 is more square-shaped (fullscreen). In decimal terms, 16:9 equals roughly 1.78 while 4:3 equals roughly 1.33. Modern displays and video use 16:9, while 4:3 is found in older content, some tablets, and presentation slides.
How do I find the aspect ratio of any image?
Check the image dimensions in pixels (width x height), then enter them into this calculator. The tool finds the greatest common divisor and divides both numbers to produce the simplified ratio. For example, a 2560x1440 image simplifies to 16:9.