Aspect Ratio Calculator
Calculate the aspect ratio of any width and height. Find equivalent dimensions for resizing without cropping.
Understanding Aspect Ratios
An aspect ratio describes the proportional relationship between width and height. When someone says "16:9", they mean for every 16 units of width, there are 9 units of height. It doesn't matter if those units are pixels, centimetres, or metres — the shape stays the same.
This matters because resizing an image without maintaining its aspect ratio distorts it. Stretching a 4:3 photo to fit a 16:9 slot squashes faces and warps buildings. The aspect ratio calculator helps you find the right dimensions for any target size while keeping the original proportions intact.
The calculator reduces your dimensions to the simplest ratio using the greatest common divisor. So 1920×1080 becomes 16:9, and 2560×1440 becomes 16:9 too — they're the same shape at different sizes.
Common Aspect Ratios
| Ratio | Decimal | Common Resolutions | Used For |
|---|---|---|---|
| 1:1 | 1.0 | 1080×1080, 500×500 | Instagram posts, profile pictures, app icons |
| 4:3 | 1.333 | 1024×768, 2048×1536 | iPad displays, classic TV, presentations |
| 3:2 | 1.5 | 1080×720, 6000×4000 | DSLR photos, Surface tablets, 35mm film |
| 16:9 | 1.778 | 1920×1080, 3840×2160 | Widescreen monitors, YouTube, TV |
| 16:10 | 1.6 | 1920×1200, 2560×1600 | MacBook displays, business monitors |
| 21:9 | 2.333 | 2560×1080, 3440×1440 | Ultrawide monitors, cinematic displays |
| 9:16 | 0.5625 | 1080×1920 | Instagram/TikTok Stories, mobile video |
| 2:3 | 0.667 | 1000×1500 | Pinterest pins, book covers, posters |
What this means for you: Before resizing any image, check which aspect ratio your target platform requires. Using the wrong ratio means either distortion or unwanted cropping.
Why Aspect Ratios Matter
Responsive Design
CSS aspect-ratio property and padding-top tricks rely on knowing the correct ratio. Getting it wrong creates layout shift when images load at unexpected dimensions.
Video Production
YouTube needs 16:9, Instagram Reels need 9:16, and TikTok needs 9:16. Shooting in the wrong ratio means cropping out parts of your footage.
Print & Photography
Standard photo print sizes (6×4, 8×6) are 3:2. Cropping a 16:9 widescreen image for print loses significant content from the sides.
Social Media
Each platform has preferred ratios — 1:1 for Instagram grid, 4:5 for feed, 9:16 for stories. Using the right ratio maximises screen space in the feed.
CSS Aspect Ratio
Modern CSS has a native aspect-ratio property that enforces ratios without padding hacks:
Modern approach
img {
aspect-ratio: 16 / 9;
width: 100%;
object-fit: cover;
}Legacy padding trick
.wrapper {
position: relative;
padding-top: 56.25%; /* 9/16 */
}
.wrapper > img {
position: absolute;
inset: 0;
}The aspect-ratio property has 95%+ browser support. Use it for image containers, video embeds, and card layouts to prevent layout shift (CLS) while images load.
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How to use this tool
Enter the width and height of your image in pixels
Read the calculated aspect ratio, decimal ratio, and orientation
Use the ratio to resize proportionally or match a target format
Common uses
- Checking if an image fits a target format like 16:9 or 1:1
- Calculating matching dimensions for proportional resizing
- Verifying aspect ratios before cropping for social media
- Finding the correct resize dimensions for print sizes
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