Image Aspect Ratio Calculator
Calculate and simplify image aspect ratios from pixel dimensions. Includes a resize calculator that maintains proportions and a reference table of common aspect ratios used in photography, video, and web design.
Image Dimensions
Ratio Details
Resize Calculator
Enter a new width or height to calculate the other dimension while preserving the aspect ratio.
Common Aspect Ratios
| Ratio | Decimal | Common Use | Example |
|---|---|---|---|
| 1:1 | 1.0000 | Square, Instagram Posts | 1080 x 1080 |
| 4:3 | 1.3333 | Classic TV, iPad, Photos | 1024 x 768 |
| 3:2 | 1.5000 | DSLR Photos, 35mm Film | 1080 x 720 |
| 16:9 (closest match) | 1.7778 | Widescreen, YouTube, HDTV | 1920 x 1080 |
| 16:10 | 1.6000 | Laptops, MacBook Displays | 1920 x 1200 |
| 21:9 | 2.3333 | Ultrawide Monitors, Cinema | 2560 x 1080 |
| 9:16 | 0.5625 | Phone Vertical, Stories, Reels | 1080 x 1920 |
How It Works
The aspect ratio is the proportional relationship between an image's width and height. This calculator simplifies the ratio by finding the Greatest Common Divisor (GCD) of both dimensions using the Euclidean algorithm, then dividing each dimension by the GCD. For example, 1920 x 1080 has a GCD of 120, so the simplified ratio is 16:9.
The decimal ratio is simply the width divided by the height, giving a single number that represents how wide the image is relative to its height. A value of 1.0 means square, greater than 1.0 means landscape, and less than 1.0 means portrait. The standard 16:9 widescreen ratio has a decimal value of approximately 1.778.
The resize calculator maintains the aspect ratio by using the proportion: new width / new height = original width / original height. When you enter a new width, the height is calculated as (new width x original height) / original width, and vice versa. Results are rounded to the nearest whole pixel.
The closest standard match is determined by comparing the decimal ratio of your image against all common ratios in the reference table and finding the one with the smallest absolute difference.
Frequently Asked Questions
Aspect ratio is the proportional relationship between the width and height of an image or screen. It is expressed as two numbers separated by a colon (e.g., 16:9). It matters because resizing an image without maintaining its aspect ratio causes distortion — stretching it horizontally or vertically. When creating content for specific platforms (YouTube, Instagram, etc.), using the correct aspect ratio ensures your content displays properly without cropping or letterboxing.
16:9 is the most common aspect ratio for video content today. It is the standard for HDTV (720p, 1080p), 4K UHD (3840 x 2160), YouTube, and most streaming platforms. Other common video ratios include 21:9 for ultrawide/cinematic content, 4:3 for classic TV footage, and 9:16 for vertical video on platforms like TikTok, Instagram Reels, and YouTube Shorts.
To resize without distortion, you must maintain the original aspect ratio. Calculate the new dimensions by keeping the ratio constant: if you know the new width, compute new height = (new width x original height) / original width. If you know the new height, compute new width = (new height x original width) / original height. Most image editors have a "constrain proportions" or "lock aspect ratio" option that does this automatically.
Each platform has preferred ratios: Instagram feed posts use 1:1 (square) or 4:5 (portrait), Instagram/Facebook Stories use 9:16, YouTube videos use 16:9, YouTube Shorts use 9:16, Twitter/X images work best at 16:9, LinkedIn images use 1.91:1, and Pinterest pins perform best at 2:3 (1000 x 1500 px). Always check the current platform guidelines as they occasionally change.