Aspect Ratio Calculator
Simplify aspect ratios, compute dimensions, and use presets for video, photo, and social media. 100% client-side.
Aspect ratio
16:9
Decimal: 1.7778 · matches 16:9
1920:1080
📊 Details
Input
1920 × 1080
Simplified ratio
16:9
GCD
120
Decimal
1.7778
📖 Aspect ratio reference
| Ratio | Decimal | Category | Common use |
|---|---|---|---|
| 16:9 | 1.778 | Video | HD, FHD, 4K, YouTube |
| 4:3 | 1.333 | Video | SD legacy, iPad |
| 21:9 | 2.333 | Video | Cinematic ultrawide |
| 9:16 | 0.563 | Video | Vertical, Stories, TikTok |
| 1.85:1 | 1.850 | Video | US theatrical widescreen |
| 2.39:1 | 2.390 | Video | Anamorphic scope |
| 1:1 | 1.000 | Video | Square |
| 3:2 | 1.500 | Photo | 35mm DSLR, classic film |
| 4:3 | 1.333 | Photo | Micro Four Thirds |
| 4:5 | 0.800 | Photo | Instagram portrait |
| 5:4 | 1.250 | Photo | Large format, 8×10 |
| 1:1 | 1.000 | Photo | Medium format, Instagram square |
| 2:3 | 0.667 | Photo | Portrait photo print |
| 5:7 | 0.714 | Photo | 5×7 print |
| 1:1 | 1.000 | Social | Instagram feed, profile |
| 4:5 | 0.800 | Social | Instagram portrait post |
| 9:16 | 0.563 | Social | Stories, Reels, TikTok |
| 16:9 | 1.778 | Social | YouTube, Twitter card |
| 1.91:1 | 1.910 | Social | Facebook, LinkedIn, OG |
| 3:1 | 3.000 | Social | Twitter header, LinkedIn banner |
| 2:1 | 2.000 | Social | Facebook event, Meetup cover |
| A-series (√2:1) | 1.414 | A4, A3, A5 (ISO 216) | |
| US Letter (17:22) | 0.773 | 8.5 × 11 in | |
| US Legal (8.5:14) | 0.607 | 8.5 × 14 in | |
| Tabloid (11:17) | 0.647 | 11 × 17 in | |
| 5:4 | 1.250 | Screens | Old LCD monitors |
| 16:10 | 1.600 | Screens | MacBook, many laptops |
| 3:2 | 1.500 | Screens | Surface, some laptops |
| 4:3 | 1.333 | Screens | iPad (4:3) |
| 1:2 | 0.500 | Other | Tall panels |
| 2:1 | 2.000 | Other | Wide banners |
| 3:4 | 0.750 | Other | Portrait photos |
🔒 100% private: All calculation happens in your browser. Your dimensions never leave your device.
About Aspect Ratio Calculator
An aspect ratio describes the proportional relationship between an image or video's width and height. It is written as W:H (e.g., 16:9) or as a decimal (1.78). Aspect ratio matters everywhere: video (16:9 widescreen, 4:3 legacy), photography (3:2 for DSLRs, 4:5 for portraits), social media (1:1 Instagram, 9:16 Stories), print (A4 is √2:1), and web design (hero images often 21:9). Knowing the ratio prevents distortion when resizing: if you change one dimension, the other must scale proportionally. This tool simplifies any W×H pair into its reduced ratio, calculates the missing dimension when you know one side and the ratio, and provides presets for every common format.
How It Works
- Aspect Ratio → Dimensions: enter a width (or height) and choose a ratio; the other dimension is computed.
- Dimensions → Aspect Ratio: enter a width and height; the ratio is simplified.
- Use presets for common formats (16:9, 4:3, 21:9, 1:1, 9:16, 3:2, 4:5, 5:4, A4, etc.).
- See the decimal value, simplified fraction, and preset name.
✨ Key Features
- ✓Simplify any width × height to its lowest ratio
- ✓Calculate missing dimension from ratio + one dimension
- ✓30+ presets (16:9, 4:3, 21:9, 1:1, 9:16, 3:2, 4:5, A4, etc.)
- ✓Shows decimal ratio (1.78, 0.75)
- ✓Shows the reduced fraction (16:9, 4:3)
- ✓Auto-detect preset name from dimensions
- ✓GCD-based simplification
- ✓Handles decimals and large numbers
- ✓Copy any value
- ✓100% client-side — no data sent to any server
🎯 Common Use Cases
- →Calculating image dimensions for a specific aspect ratio
- →Checking whether an image matches a target ratio (e.g., YouTube thumbnail)
- →Resizing videos without distortion
- →Planning web layouts (hero images, cards, thumbnails)
- →Preparing social media posts at the correct ratio
- →Understanding print sizes (A4 is √2:1)
- →Scaling images for responsive design
- →Verifying aspect ratios of uploaded files
💡 Advanced Tips & Pro Insights
- ▸Common video ratios: 16:9 (widescreen HD/4K), 4:3 (legacy SD), 21:9 (cinematic ultrawide), 9:16 (vertical/Stories), 1:1 (square).
- ▸Common photo ratios: 3:2 (35mm DSLR), 4:3 (Micro Four Thirds), 1:1 (medium format), 4:5 (portrait social), 5:4 (large format).
- ▸Social media: Instagram square 1:1, Instagram portrait 4:5, Instagram Stories/TikTok 9:16, YouTube thumbnail 16:9, Twitter header 3:1.
- ▸Print sizes: A4 is 210×297 mm ≈ 1:1.414 (√2). US Letter is 8.5×11 in = 17:22. Photo prints: 4×6 = 2:3, 5×7 ≈ 5:7, 8×10 = 4:5.
- ▸When resizing, keep the aspect ratio to avoid distortion. If you must fit into a different ratio, crop (better) or letterbox (add bars).
Frequently Asked Questions
Is this aspect ratio calculator free?▾
Yes, this aspect ratio calculator is completely free with no signup, email, or usage limits.
Is my data safe?▾
Yes, 100% safe. All calculation happens in your browser. No data is sent to any server.
What is an aspect ratio?▾
An aspect ratio is the proportional relationship between width and height, written as W:H (e.g., 16:9) or as a decimal (1.78). It describes the shape of an image or video, independent of size.
How do I calculate aspect ratio?▾
Divide the width by the height and simplify the fraction. For example, 1920×1080 → 1920/1080 = 1.777... → 16:9. This tool simplifies automatically using the greatest common divisor.
How do I resize an image without distortion?▾
Keep the aspect ratio constant. If you know one dimension, multiply or divide by the ratio to get the other. For example, a 16:9 image at width 1920 has height = 1920 × 9/16 = 1080.
What are the most common aspect ratios?▾
Video: 16:9 (standard HD/4K), 21:9 (cinematic), 9:16 (vertical). Photography: 3:2, 4:3, 1:1. Social media: 1:1 (Instagram square), 4:5 (Instagram portrait), 9:16 (Stories).
What is the aspect ratio of A4 paper?▾
A4 is 210×297 mm, which simplifies to 1:√2 (approximately 1:1.4142). This is the basis of the ISO 216 paper size standard — each size is half the previous one while maintaining the same ratio.
Can I enter a ratio and get dimensions?▾
Yes. Enter one dimension (width or height) and pick a ratio, and this tool computes the other dimension. Perfect for planning a canvas size for a specific format.