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 to Use This Tool
- Enter the image width in pixels.
- Enter the image height in pixels.
- View the simplified aspect ratio (e.g. 16:9) and decimal ratio instantly.
- Check Ratio Details for orientation, total pixels, megapixels, and the closest standard ratio match.
- Use the Resize Calculator to enter a new width or height — the other dimension is calculated automatically to preserve the same proportions.
- Compare your ratio against the Common Aspect Ratios table to see typical use cases like YouTube, Instagram, or DSLR photos.
Formula & How It Works
Simplified Ratio (GCD Method)
ratio = (width ÷ GCD(width, height)) : (height ÷ GCD(width, height))The tool finds the Greatest Common Divisor of the width and height using the Euclidean algorithm, then divides both dimensions by it. For example, 1920×1080 has GCD 120, giving 16:9.
Decimal Ratio
decimalRatio = width ÷ heightA value of 1.0 means square, greater than 1.0 means landscape, less than 1.0 means portrait. 16:9 equals approximately 1.778.
Proportional Resize Formula
newHeight = (newWidth × originalHeight) ÷ originalWidth (or vice versa)Keeping the ratio new width ÷ new height equal to original width ÷ original height prevents the image from stretching or distorting.
Practical Examples & Common Use Cases
Simplifying a 1920×1080 image
GCD(1920, 1080) = 120. Simplified ratio = 1920/120 : 1080/120 = 16:9, the standard widescreen ratio, with a decimal value of 1.7778.
Resizing a photo while keeping proportions
An original image is 3000×2000 (ratio 3:2). Entering a new width of 1200 gives newHeight = (1200 × 2000) ÷ 3000 = 800, so the resized image is 1200×800.
Finding the closest standard ratio for a custom image
A 2560×1600 image has a decimal ratio of 1.6, which is closest to the 16:10 standard (1.6 exactly) — commonly used for laptop and MacBook displays.
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.