Aspect Ratio Calculator
Calculate aspect ratios, resize dimensions proportionally, and get CSS aspect-ratio values
Proportional Resize
aspect-ratio: 16 / 9;Aspect Ratio Calculator
Calculate aspect ratios, resize dimensions proportionally, and get CSS aspect-ratio values
Features
- Calculate aspect ratio from any width and height
- Proportional resize — enter new width or height to auto-calculate the other
- Common ratio presets (16:9, 4:3, 1:1, 21:9, etc.)
- Visual aspect ratio preview
- CSS aspect-ratio property output
- Swap dimensions with one click
- 100% client-side processing
How to use
- Enter width and height to calculate the aspect ratio.
- Or click a preset ratio button.
- Use the Proportional Resize section to find new dimensions.
- Copy the CSS aspect-ratio value for your stylesheets.
Tips & Best Practices
- Use 16:9 for standard video and presentations.
- Use 1:1 for social media profile pictures and Instagram posts.
- The CSS aspect-ratio property is supported in all modern browsers.
FAQ
What is an aspect ratio?
An aspect ratio is the proportional relationship between width and height. For example, 16:9 means for every 16 units of width, there are 9 units of height.
What aspect ratio is best for video?
16:9 is the standard for HD video and most screens. 21:9 is used for ultrawide/cinematic content. 9:16 is standard for vertical/mobile video.
How does proportional resize work?
Enter either a new width or new height, and the calculator will compute the other dimension to maintain the same aspect ratio — no stretching or distortion.
How do I calculate aspect ratio for responsive images?
Divide the original width by the height to get the ratio as a decimal, or use the calculator to express it as W:H. For responsive design, apply the CSS aspect-ratio property to the container so the browser reserves space and avoids layout shift while images load.
What is the difference between 16:9 and 16:10?
16:9 (1.78:1) is the standard for HD/4K TVs, YouTube, and most monitors, while 16:10 (1.6:1) is slightly taller and common on productivity-focused laptops and older Apple displays. The extra vertical pixels in 16:10 are useful for code, documents, and design work where more rows are visible at once.
Why are my calculated dimensions not whole numbers?
Aspect ratios often produce fractional pixel results when scaling — for example, a 1920x1080 image resized to 500px wide yields 281.25px tall. The calculator rounds to the nearest integer for display, but you can adjust the input width or height by 1-2 pixels to get clean whole-number output.
Does the CSS aspect-ratio property work in all browsers?
Yes, the CSS aspect-ratio property is supported in all modern browsers (Chrome 88+, Firefox 89+, Safari 15+) and is now considered baseline. For legacy browser support, you can fall back to the classic padding-bottom percentage hack inside a wrapper div.
Is this calculator free and is my data private?
Yes, the aspect ratio calculator is completely free with no signup required. All calculations run locally in your browser using JavaScript — no dimensions, ratios, or values are ever sent to a server.