Aspect Ratio Calculator
Find the aspect ratio of any image or video, resize dimensions while keeping proportions, and look up the correct sizes for YouTube, Instagram, TikTok, and more. All calculations happen instantly in your browser.
Aspect Ratio Calculator
Enter width and height to see the ratio.
Resize Image to Aspect Ratio
Enter your original dimensions, then fill in either the new width or new height. The other value is calculated automatically.
Enter original dimensions and one new dimension.
16:9 Aspect Ratio Calculator
Enter a value to calculate the other dimension.
Common 16:9 Resolutions
| Width | Height | Label |
|---|---|---|
| 640px | 360px | 360p |
| 854px | 480px | 480p |
| 1280px | 720px | 720p HD |
| 1920px | 1080px | 1080p Full HD |
| 2560px | 1440px | 1440p QHD |
| 3840px | 2160px | 4K UHD |
4:3 Aspect Ratio Calculator
Enter a value to calculate the other dimension.
Common 4:3 Resolutions
| Width | Height | Label |
|---|---|---|
| 800px | 600px | SVGA |
| 1024px | 768px | XGA |
| 1400px | 1050px | SXGA+ |
| 2048px | 1536px | iPad Retina |
Ratio to Pixels Calculator
Enter an aspect ratio (e.g. 16:9, 16/9, or 1.78) and one dimension to find the other.
Enter a ratio and one dimension.
Image Crop Calculator
Find the largest crop that fits a target aspect ratio inside your original image, centered.
Enter original dimensions and a target ratio.
Common Screen Resolutions by Aspect Ratio
| Resolution | Ratio | Common Use |
|---|---|---|
| 640×360 | 16:9 | Low-res web video |
| 854×480 | 16:9 | 480p standard definition |
| 1280×720 | 16:9 | HD (720p), YouTube minimum |
| 1920×1080 | 16:9 | Full HD (1080p), most common |
| 2560×1440 | 16:9 | QHD / 2K monitor |
| 3840×2160 | 16:9 | 4K UHD, streaming & TV |
| 800×600 | 4:3 | Legacy web & presentations |
| 1024×768 | 4:3 | XGA standard monitor |
| 1400×1050 | 4:3 | SXGA+ display |
| 2048×1536 | 4:3 | iPad (Retina) display |
| 1080×1080 | 1:1 | Instagram square post |
| 1080×1920 | 9:16 | Stories, Reels, TikTok |
| 2560×1080 | 21:9 | Ultrawide monitor |
| 3440×1440 | 21:9 | Ultrawide QHD |
| 4000×6000 | 2:3 | Full-frame DSLR photo |
Aspect Ratio Guide
What is 16:9 aspect ratio?
16:9 is the standard widescreen aspect ratio used in modern televisions, computer monitors, YouTube videos, and streaming services. It produces an image that is 1.78× wider than it is tall. Common 16:9 resolutions include 1280×720 (HD), 1920×1080 (Full HD), 2560×1440 (QHD), and 3840×2160 (4K).
What is 4:3 aspect ratio?
4:3 is the traditional aspect ratio used in older televisions, early computer monitors, and standard-definition video. It produces an image that is 1.33× wider than it is tall — closer to a square than 16:9. Common 4:3 resolutions include 800×600, 1024×768, and 2048×1536 (iPad Retina).
What is 1:1 aspect ratio?
1:1 is a perfect square aspect ratio. It is commonly used for Instagram feed posts, album artwork, and profile photos. Any resolution where width equals height is 1:1 — for example, 1080×1080, 500×500, or 2000×2000.
What aspect ratio is 1920×1080?
1920×1080 is a 16:9 aspect ratio. It is the standard Full HD (1080p) resolution, used by most modern TVs, monitors, and streaming platforms. To verify: GCD(1920, 1080) = 120; 1920÷120 = 16, 1080÷120 = 9.
What aspect ratio is 1280×720?
1280×720 is a 16:9 aspect ratio. It is the standard HD (720p) resolution. GCD(1280, 720) = 80; 1280÷80 = 16, 720÷80 = 9.
What aspect ratio should I use for YouTube?
YouTube recommends 16:9 for all videos. Upload at minimum 1280×720 (HD) and ideally 1920×1080 (Full HD) or higher. Thumbnails should also be 16:9 at 1280×720 pixels.
What aspect ratio should I use for Instagram?
For Instagram feed posts, use 1:1 (square, 1080×1080) or 4:5 (portrait, 1080×1350) to maximise screen space. For Stories and Reels, use 9:16 (1080×1920). Landscape posts use 1.91:1 (1080×566), though portrait tends to perform better.
Why use our online Aspect Ratio Calculator?
Find the correct width or height for any aspect ratio — 16:9, 4:3, 1:1, or custom — without doing the math manually. Useful for resizing images, setting video dimensions, and responsive design.
How to use Aspect Ratio Calculator
- 1Enter your image dimensions
Type the width and height in pixels into the Aspect Ratio Calculator. The simplified ratio, decimal value, and category label update instantly.
- 2Use the resize tool to scale dimensions
Enter your original width and height, then fill in either the new width or new height. The calculator finds the missing dimension while preserving the exact ratio.
- 3Pick a platform from the social media guide
Select a platform like Instagram Post or YouTube Thumbnail from the dropdown. You'll see the recommended ratio, pixel dimensions, and a visual shape preview.
- 4Check if your image fits a platform
Enter your image's current dimensions in the fit-check field below the platform selector. The tool tells you instantly whether it fits or what will be cropped.
- 5Use the crop calculator for precise cropping
Enter your original image size and desired target ratio. The tool shows you the maximum crop dimensions and how many pixels to remove from each side.
Why aspect ratio matters — the mathematics of visual composition
Aspect ratio describes the proportional shape of an image or screen. It is expressed as width:height — a 16:9 image is 1.78 times wider than it is tall, while a 4:3 image is 1.33 times wider. These ratios define how content is composed, framed, and displayed.
The choice of aspect ratio is not arbitrary — it shapes viewer perception. Widescreen ratios (16:9, 21:9) evoke cinematic breadth and are used for immersive storytelling. Square and tall ratios (1:1, 4:5, 9:16) fill mobile screens and create intimate, focused compositions. Landscape photography traditionally uses 3:2 (the native ratio of full-frame DSLR sensors, inherited from 35mm film), while portrait photography uses 3:2 or 4:5.
Mathematically, aspect ratio is the simplified ratio of width to height. To simplify, divide both by their GCD. 1920 and 1080 share a GCD of 120, giving 16:9. 3024 × 4032 (common iPhone portrait photo) shares GCD of 1008, giving 3:4. Understanding this lets you compare any two images and immediately assess whether they have compatible shapes for a layout.
Social media image dimensions — a platform-by-platform guide
Each platform has specific recommended dimensions. Using the wrong ratio results in automatic cropping that may cut off important elements.
Instagram Feed Square: 1080 × 1080 px (1:1). Instagram Feed Portrait: 1080 × 1350 px (4:5). Instagram Reels and Stories: 1080 × 1920 px (9:16). Instagram Carousel: all images should match the ratio of the first image in the series.
YouTube Thumbnail: 1280 × 720 px (16:9). YouTube Shorts: 1080 × 1920 px (9:16). Facebook Feed: 1200 × 630 px (1.91:1) optimized; square 1080 × 1080 px also works well. Facebook Cover: 820 × 312 px desktop (2.63:1).
LinkedIn Post Image: 1200 × 627 px (1.91:1). LinkedIn Article Cover: 1920 × 1080 px (16:9). Twitter/X Post Image: 1200 × 675 px (16:9) for single images; 1200 × 628 px for link preview cards.
TikTok: 1080 × 1920 px (9:16). Pinterest Pin: 1000 × 1500 px (2:3) is the recommended vertical format.
Cropping vs letterboxing vs pillarboxing — how platforms handle wrong ratios
When an image or video does not match the target aspect ratio, platforms handle the discrepancy in one of three ways.
Cropping removes pixels from the edges to fit the target ratio. A landscape 16:9 image displayed in a 1:1 square slot loses the sides — the left and right portions are cut off. This is the default behavior on most social media platforms and is why portrait-oriented content often performs better on mobile-first platforms: it fills more of the screen without cropping.
Letterboxing (or pillarboxing) preserves the full image by adding black bars. Letterboxing adds bars at the top and bottom (for wide images in a taller container). Pillarboxing adds bars at the sides (for tall images in a wider container). This maintains the original composition but reduces the effective display area and may look amateurish on platforms that display images without bars.
Smart cropping algorithms (used by Squarespace, Cloudinary, and some social platforms) attempt to identify the focal point of an image — faces, prominent subjects — and center the crop around that point rather than center-cropping mechanically. Always check how your specific image is cropped by uploading a test version before publishing important content.
Frequently Asked Questions
What is aspect ratio?
- Aspect ratio is the proportional relationship between an image's width and height, expressed as two numbers separated by a colon (e.g. 16:9). It describes the shape of an image — wide, square, or tall — without specifying exact dimensions. The same 16:9 ratio applies to both 1280×720 and 1920×1080.
How do I calculate aspect ratio?
- To calculate aspect ratio, divide both the width and height by their greatest common divisor (GCD). For example, 1920×1080: the GCD of 1920 and 1080 is 120, so 1920÷120=16 and 1080÷120=9, giving a ratio of 16:9. This calculator does all of that automatically.
What is the aspect ratio of 1920×1080?
- 1920×1080 is a 16:9 aspect ratio. It is the standard resolution for Full HD (1080p) video, used by YouTube, streaming services, and most modern monitors and televisions.
What is 16:9 in pixels?
- 16:9 is a ratio, not a fixed pixel count. Common 16:9 resolutions include 1280×720 (HD), 1920×1080 (Full HD), 2560×1440 (QHD), and 3840×2160 (4K UHD). Any width divisible by 16 — paired with a height that is 9/16 of that width — produces a valid 16:9 image.
How do I resize an image without losing quality?
- To resize without quality loss, maintain the original aspect ratio exactly. Use this calculator's Resize tool: enter the original dimensions, fill in the new width or height, and the tool gives you the exact matching dimension. Then use image editing software to resize to those exact pixel values.
What aspect ratio is best for YouTube?
- YouTube recommends 16:9 for all videos. This is the standard widescreen format used on most TVs and monitors. The minimum recommended resolution is 1280×720, and the ideal upload resolution is 1920×1080 (Full HD) or 3840×2160 (4K).
What aspect ratio is best for Instagram?
- Instagram supports multiple ratios: 1:1 (square) for feed posts, 4:5 (portrait, 1080×1350) for taller feed posts that take up more screen space, and 9:16 (1080×1920) for Stories and Reels. Portrait posts (4:5) generally get more engagement on feed because they occupy more vertical screen area.
What is the difference between 16:9 and 4:3?
- 16:9 is a widescreen format used in modern TVs, YouTube, and most digital video. 4:3 is the older square-ish format used by CRT televisions, early computer monitors, and standard-definition TV. A 16:9 image is noticeably wider and shorter than a 4:3 image at the same height.
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Social Media Image Size Calculator
Aspect Ratio
1:1
Recommended Size
1080×1080px
File size tip
Max 30 MB, JPG or PNG
Shape preview
Will my image fit?