Aspect Ratio:
Table of Contents
What is aspect ratio?
Aspect ratio is the proportional relationship between the width and height of a screen, image, or video. It is written as two numbers separated by a colon — such as 16:9 or 4:3 — and tells you how wide something is relative to its height.
How to calculate aspect ratio
To calculate the aspect ratio of any width and height, you need to find the greatest common divisor (GCD) of the two numbers, then divide both by it to get the simplified ratio.
For example, a resolution of 1920×1080:
GCD(1920, 1080) = 120
1920 ÷ 120 = 16
1080 ÷ 120 = 9
Aspect ratio = 16:9
The calculator above does this automatically — just enter the width and height in pixels and click Calculate.
Why does aspect ratio matter?
Aspect ratio affects how images and video are displayed across different screens and platforms. Using the wrong aspect ratio can result in letterboxing (black bars), cropping, or distortion. Getting it right is essential in video production, web design, photography, and any creative work where visual proportions matter.
Common aspect ratios
| Aspect Ratio | Common Resolution | Use Case |
|---|---|---|
| 16:9 | 1920×1080 / 3840×2160 | HD/4K video, YouTube, most monitors |
| 4:3 | 1024×768 / 1600×1200 | Traditional TV, older monitors |
| 1:1 | 1080×1080 | Instagram square, profile images |
| 21:9 | 2560×1080 / 3440×1440 | Ultrawide monitors, cinematic video |
| 3:2 | 3000×2000 | DSLR cameras, 35mm photography |
| 9:16 | 1080×1920 | Portrait video, TikTok, Instagram Stories |
| 4:5 | 1080×1350 | Instagram portrait posts |
When to use the aspect ratio calculator
This calculator is useful any time you need to understand or verify the proportions of an image or display. Common scenarios include:
- Checking if a video is in 16:9 before uploading to YouTube
- Designing responsive layouts for websites
- Resizing images while keeping proportions consistent
- Configuring display or monitor settings
- Ensuring social media assets are sized correctly for each platform
FAQs
Aspect ratio is the proportional relationship between the width and height of an image, screen, or video. It is expressed as two numbers separated by a colon, such as 16:9 or 4:3, representing width to height.
1920x1080 (Full HD or 1080p) has a 16:9 aspect ratio. Dividing both dimensions by their greatest common divisor of 120 gives 16 and 9.
The most common aspect ratio for video today is 16:9, which is the standard for HD and 4K television, YouTube, and most modern displays.
To calculate the aspect ratio from pixel dimensions, find the greatest common divisor (GCD) of the width and height, then divide both values by the GCD. For example, 1280x720 divides by 80 to give 16:9.
The 4:3 aspect ratio was the standard for traditional television and early computer monitors. It is still used in some photography formats, older educational content, and certain iPad models.
Digital SLR cameras commonly shoot in 3:2, Micro Four Thirds cameras use 4:3, and medium format cameras often use 1:1 (square). Many smartphones now shoot in 4:3 or 16:9 depending on the mode.