Aspect Ratio Calculator
Calculate aspect ratios, resize images and video proportionally, and find the simplified ratio for any resolution. Supports all common ratios including 16:9, 4:3, 21:9, and more.
Calculate from Ratio
Select a preset ratio or enter a custom one, then enter either width or height to calculate the other dimension.
Find Aspect Ratio
Enter a width and height to find the simplified aspect ratio.
Resize Proportionally
Enter original dimensions and a new width or height to calculate the other dimension while maintaining the aspect ratio.
How to Use the Aspect Ratio Calculator
- Calculate from Ratio — Select a preset ratio (16:9, 4:3, etc.) or enter a custom ratio, then type a width or height to automatically calculate the missing dimension.
- Find Aspect Ratio — Enter any width and height (e.g., 1920 x 1080) to find the simplified aspect ratio (16:9) and decimal ratio (1.78:1).
- Resize Proportionally — Enter original dimensions and a new width or new height. The tool calculates the other dimension so the image or video maintains its original proportions.
Common Aspect Ratios Explained
Here are the most widely used aspect ratios across photography, video, displays, and social media.
| Ratio | Decimal | Common Use |
|---|---|---|
| 1:1 | 1.00 | Square — Instagram posts, profile pictures, album art |
| 4:3 | 1.33 | Standard definition TV, iPad displays, older monitors |
| 3:2 | 1.50 | 35mm film, DSLR photos, Microsoft Surface |
| 16:9 | 1.78 | Widescreen HD/4K — YouTube, Netflix, most monitors and TVs |
| 16:10 | 1.60 | MacBook displays, WUXGA monitors |
| 21:9 | 2.33 | Ultrawide monitors, cinematic video |
| 9:16 | 0.56 | Vertical video — TikTok, Instagram Reels, YouTube Shorts |
| 2.35:1 | 2.35 | Anamorphic widescreen cinema (CinemaScope) |
| 4:5 | 0.80 | Instagram portrait posts (1080x1350) |
| 2:3 | 0.67 | Pinterest pins (1000x1500), portrait photography |
Aspect Ratios for Social Media
Each social media platform has recommended image and video sizes. Use these dimensions for the best results on each platform.
| Platform | Recommended Size | Aspect Ratio |
|---|---|---|
| Instagram Post (Square) | 1080 x 1080 | 1:1 |
| Instagram Post (Portrait) | 1080 x 1350 | 4:5 |
| Instagram Story / Reel | 1080 x 1920 | 9:16 |
| YouTube Thumbnail | 1280 x 720 | 16:9 |
| Twitter / X Post | 1200 x 675 | 16:9 |
| Facebook Post | 1200 x 630 | 1.91:1 |
| LinkedIn Post | 1200 x 627 | 1.91:1 |
| TikTok | 1080 x 1920 | 9:16 |
| Pinterest Pin | 1000 x 1500 | 2:3 |
Standard Video Resolutions
These are the most common video resolutions used in broadcasting, streaming, and content creation.
| Name | Resolution | Ratio |
|---|---|---|
| 720p (HD) | 1280 x 720 | 16:9 |
| 1080p (Full HD) | 1920 x 1080 | 16:9 |
| 1440p (2K / QHD) | 2560 x 1440 | 16:9 |
| 4K (Ultra HD) | 3840 x 2160 | 16:9 |
| 8K (Full Ultra HD) | 7680 x 4320 | 16:9 |
Frequently Asked Questions
An aspect ratio is the proportional relationship between the width and height of an image, video, or screen. It is expressed as two numbers separated by a colon, such as 16:9 or 4:3. The first number represents the width and the second represents the height. A 16:9 ratio means the width is 1.78 times the height.
The most common aspect ratio for video is 16:9 (widescreen). It is the standard for YouTube, most TVs, computer monitors, and streaming platforms. Common resolutions in 16:9 include 1280x720 (HD), 1920x1080 (Full HD), 2560x1440 (2K), and 3840x2160 (4K).
To calculate the aspect ratio, find the Greatest Common Divisor (GCD) of the width and height, then divide both values by it. For example, for 1920x1080: the GCD of 1920 and 1080 is 120. Dividing both by 120 gives 16:9. This tool does it automatically.
To resize proportionally, calculate the scale factor by dividing the new dimension by the original. For example, if the original is 1920x1080 and you want the new width to be 1280, the scale factor is 1280/1920 = 0.6667. Multiply the original height by this factor: 1080 x 0.6667 = 720. Use the Resize Proportionally section above to do this instantly.
Instagram supports multiple aspect ratios. Square posts use 1:1 (1080x1080). Portrait posts use 4:5 (1080x1350). Landscape posts use 1.91:1 (1080x566). Stories and Reels use 9:16 (1080x1920). For maximum engagement, 4:5 portrait is recommended for feed posts as it takes up more screen space.
16:9 is the standard widescreen ratio used by most TVs, monitors, and video content (1920x1080, 3840x2160). 16:10 is slightly taller and is commonly used in laptops, especially MacBooks (2560x1600). The 16:10 ratio provides more vertical space, which is useful for productivity tasks like reading documents and browsing the web.
1920x1080 has an aspect ratio of 16:9. This is the standard Full HD (1080p) resolution used by most monitors, TVs, and online video platforms including YouTube and Netflix. It has been the dominant display resolution since the transition from 4:3 standard definition.