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Use Calculate size when you know the ratio and one pixel dimension. Use Calculate ratio when you already know width and height.
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Free image tool
Free Aspect Ratio Calculator
Calculate pixel dimensions from a ratio, or reduce any image size to its simplest aspect ratio. Keep photos, videos, and AI image outputs proportional without stretching.
Calculation mode
Ratio size
Pixel dimensions
Result
Pixel size
1,920 × 1,080Aspect ratio
16:9Decimal
1.7778CSS
aspect-ratio: 16 / 9;Aspect ratio preview
16:916:9
1,920 × 1,080
Common aspect ratios
How to use the aspect ratio calculator
Enter your values
Type a ratio such as 16:9 or enter pixel dimensions such as 1920 x 1080.
Copy the result
Use the calculated pixel size, simplified ratio, decimal value, or CSS aspect-ratio value in your project.
Aspect ratio formulas
Use these formulas when you need to calculate image or video dimensions manually.
Find height from width
Height = (Width x Ratio Height) / Ratio Width. Example: 1920 x 9 / 16 = 1080.
Find width from height
Width = (Height x Ratio Width) / Ratio Height. Example: 1080 x 16 / 9 = 1920.
What is aspect ratio?
Aspect ratio is the proportional relationship between width and height. It describes shape, while resolution describes the actual number of pixels.
Ratio describes shape
A 16:9 image keeps the same shape whether it is 1280 x 720, 1920 x 1080, or 3840 x 2160.
Resolution describes pixels
Two images can share the same aspect ratio but have very different pixel counts and export quality.
Locked ratios prevent stretching
When you resize width and height proportionally, people, products, and graphics keep their natural shape.
Useful for AI image generation
Calculate the exact target canvas before generating or extending an image so the result fits your final platform.
Common aspect ratios and uses
Pick a ratio based on where the final image or video will be published.
16:9 widescreen
Standard for YouTube videos, HD TV, desktop video, and many presentation formats.
1:1 square
Works well for avatars, product thumbnails, and balanced social media feed posts.
9:16 vertical
Best for TikTok, Instagram Reels, YouTube Shorts, and full-screen mobile stories.
4:5 portrait
A strong option for Instagram feed images and vertical ads that need more screen space.
4:3 standard
Used by older displays, some cameras, slides, and legacy video formats.
21:9 ultrawide
Used for cinematic crops, ultrawide monitors, immersive banners, and game visuals.
Frequently Asked Questions
It is a tool that calculates the relationship between width and height. You can use it to find a missing pixel dimension or reduce a pixel size to a simple ratio.
Create images at the exact size you need
Use the calculator to choose your target dimensions, then generate or extend images with PixUnblur tools.
Free ratio calculator
Pixel-perfect dimensions
No distortion