Web Tools
Aspect Ratio Calculator
Calculate, simplify, and convert aspect ratios. Resize dimensions while preserving proportions with common presets. Runs entirely in your browser — your data never leaves your machine.
aspect-ratio dimensions resize responsive image video css developer-tools
Published May 28, 2026
All interactive tools run entirely in your browser. Your data never leaves your device.
How It Works
Enter width and height to calculate the simplified aspect ratio and decimal value. Use the resize calculator to find new dimensions that maintain the same proportions.
Features
- Ratio simplification: automatically reduces dimensions to simplest ratio (e.g. 1920×1080 → 16:9)
- Decimal display: shows the ratio as a decimal for CSS calculations
- Common presets: quick-select 16:9, 4:3, 21:9, 1:1, 3:2, 5:4, 9:16, 2:1
- Resize calculator: enter a new width or height, get the other dimension preserving ratio
- Copy result: one-click copy of dimensions and ratio
- Private: runs entirely in the browser — no data transmitted
Common Aspect Ratios
| Ratio | Decimal | Common Use |
|---|---|---|
| 16:9 | 1.7778 | HD video, monitors, YouTube |
| 4:3 | 1.3333 | Classic TV, iPad |
| 21:9 | 2.3333 | Ultrawide monitors, cinema |
| 1:1 | 1.0000 | Instagram square, profile photos |
| 3:2 | 1.5000 | DSLR photos, MacBook displays |
| 9:16 | 0.5625 | Mobile video, Stories, TikTok |
Use Cases
- Calculating responsive image dimensions for web design
- Resizing video or banner assets while maintaining proportions
- Finding the correct CSS
aspect-ratiovalue - Converting between standard display resolutions