Aspect Ratio Calculator – Calculate & Convert Ratios Free
Calculate aspect ratios, scale dimensions, and find equivalent sizes for any image or video online. Includes common presets, social media sizes, and a visual proportion display—free and instant.
Runs in your browser
WebAssembly, no server
No signup required
Open and use instantly
Files stay private
Nothing leaves your device
How It Works
To find a ratio: enter the width and height of your image or video
To find missing dimensions: select a preset ratio or enter a custom ratio, then enter either width or height
The missing dimension or ratio is calculated instantly
Key Features
- Calculate aspect ratio from width and height
- Get width or height from a known ratio and one dimension
- Common preset ratios (16:9, 4:3, 1:1, 9:16, 3:2, 21:9)
- Ratio simplification using GCD
- Decimal and pixel precision output
- Copy ratio or dimensions to clipboard
- No sign-up required
- Free with no limits
- Mobile-friendly
- Instant calculations
About This Tool
Our Aspect Ratio Calculator helps you find, convert, and apply aspect ratios for images, videos, screens, and designs — with instant calculations and no formulas required.
What Is Aspect Ratio?
Aspect ratio is the proportional relationship between width and height, expressed as W:H (e.g., 16:9). The same ratio can apply to any size: 1920×1080, 1280×720, and 640×360 are all 16:9.
Common Aspect Ratios
| Ratio | Common Use |
|-------|------------|
| 16:9 | Widescreen video, YouTube, TV |
| 4:3 | Traditional TV, old monitors |
| 1:1 | Instagram posts, profile photos |
| 9:16 | Mobile video, TikTok, Stories |
| 21:9 | Ultrawide monitors, cinema |
| 3:2 | DSLR photos, MacBook screens |
| 4:5 | Instagram portrait |
Two Calculation Modes
1. From dimensions: enter width and height → get the simplified ratio
2. From ratio: enter the ratio and one dimension → get the missing dimension
Use Cases
- Resize images without distortion
- Find correct crop dimensions for social media
- Calculate video export dimensions
- Verify screen or print proportions
Frequently Asked Questions
For every 16 units of width, the height is 9 units. Standard widescreen HD video (1920×1080, 1280×720) is 16:9.
Enter your known dimension and the tool calculates the other dimension to maintain the exact ratio.
1080×1920 simplifies to a 9:16 aspect ratio — standard for vertical/portrait mobile video (TikTok, Instagram Stories).
Standard 4K (3840×2160) is 16:9 — the same ratio as 1080p HD, just at four times the pixel density.
YouTube uses 16:9. Videos in 4:3 will have black bars on the sides when played on YouTube.
Yes — completely free with no sign-up.
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