Understanding Aspect Ratios
An aspect ratio describes the proportional relationship between the width and height of a rectangle. When you see a value like 16:9, it means that for every 16 units of width there are 9 units of height. This ratio stays the same regardless of the actual pixel dimensions — both 1920 x 1080 and 3840 x 2160 share the 16:9 aspect ratio.
Designers, video editors, and marketers need to work with aspect ratios constantly — from resizing images for social media to setting up video exports and responsive layouts.
Common Aspect Ratios and Where They Are Used
The standard widescreen ratio. Used by YouTube, most TVs, monitors, and video conferencing tools. Common resolutions: 1920 x 1080 (Full HD), 2560 x 1440 (QHD), 3840 x 2160 (4K).
The classic TV and presentation format. Still widely used for slides (1024 x 768) and iPad displays.
A perfect square. Popular for Instagram feed posts, profile pictures, and album artwork. Common size: 1080 x 1080.
Vertical/portrait widescreen. The native format for Instagram Stories, TikTok, YouTube Shorts, and Snapchat. Standard: 1080 x 1920.
Ultra-widescreen / cinematic ratio. Used by ultrawide monitors and many feature films. Common resolution: 2560 x 1080.
The classic photography ratio used by 35mm film. Found in Microsoft Surface devices and some Chromebooks.
How to Calculate Aspect Ratio
The mathematical approach uses the Greatest Common Divisor (GCD). Take the width and height in pixels, find their GCD, and divide both values by it:
For example, with 1920 x 1080: the GCD is 120. So 1920 / 120 = 16 and 1080 / 120 = 9, giving 16:9.
Social Media Image Size Guide 2026
| Platform | Format | Size (px) | Ratio |
|---|---|---|---|
| Instagram Feed | Square | 1080 x 1080 | 1:1 |
| Instagram Story | Vertical | 1080 x 1920 | 9:16 |
| YouTube Thumbnail | Landscape | 1280 x 720 | 16:9 |
| Twitter/X Post | Landscape | 1200 x 675 | 16:9 |
| LinkedIn Post | Landscape | 1200 x 627 | 1.91:1 |
| Facebook Cover | Banner | 820 x 312 | 2.63:1 |
Frequently Asked Questions
What is an aspect ratio?
An 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. The first number represents width and the second represents height.
How do I calculate aspect ratio from pixel dimensions?
Divide both the width and height by their greatest common divisor (GCD). For example, 1920 x 1080: the GCD of 1920 and 1080 is 120, so 1920/120 = 16 and 1080/120 = 9, giving an aspect ratio of 16:9.
What aspect ratio should I use for social media images?
It depends on the platform: Instagram feed posts use 1:1 (square) or 4:5 (portrait), Instagram Stories and Reels use 9:16 (vertical), YouTube thumbnails and videos use 16:9 (landscape), and Twitter/X images work best at 16:9.
What is the difference between 16:9 and 16:10?
16:9 is the standard widescreen ratio used by most TVs, monitors, and video platforms. 16:10 is slightly taller and is commonly used by productivity-focused laptop displays, including MacBook screens at 2560 x 1600.
How do I resize an image while keeping the aspect ratio?
Change only one dimension (width or height) and calculate the other using the formula: new height = new width / (original width / original height). This tool does this calculation automatically when you enter either a new width or a new height.