# Aspect Ratio Calculator

> Compute the aspect ratio of any width × height, and resize to a target width or fit inside a maximum box.

URL: https://uttir.com/aspect-ratio-calculator
Categories: image-tools
Privacy: All math runs locally. No image is uploaded.

## About

Aspect ratio describes the proportional relationship between width and height. It is the magic number behind "why does this photo look squished?" and "what resolution do I need for an Instagram Reel?".

Enter any two dimensions and the tool reduces them to their simplest ratio (e.g. 1920×1080 → 16:9). You can then resize to a target width, fit inside a maximum box, or look up common preset ratios for social media, print, and video.

## How to use

1. **Enter width and height** — In any unit — pixels, mm, inches. The ratio is unitless.
2. **Read the reduced ratio** — The tool uses the GCD of width and height to show the cleanest form.
3. **Resize or fit** — Pick a target width or max bounds to see the new dimensions.

## Examples

### 1920×1080 video

Full HD video, reduced.

Output:

```
16:9
```

### 1080×1920 Reel

Vertical video for Instagram Reels / TikTok.

Output:

```
9:16
```

## FAQ

### What is the "reduced" ratio?

Every pixel-perfect ratio can be expressed as a simplified fraction. The reduced form is the version with the smallest whole numbers — 1920×1080 reduces to 16:9 because the GCD of 1920 and 1080 is 120.

### Why does my 1080×1080 Instagram post have ratio 1:1 but my 1080×1350 post has 4:5?

Both are common Instagram aspect ratios. 1:1 is the original square format, 4:5 takes up more vertical space in the feed and gets more attention. Use the preset list to confirm what you are about to publish.

### What is the difference between 16:9 and 1.78:1?

They are the same aspect ratio written two ways. 16:9 is the common short form; 1.78:1 is the decimal form. Both describe the ratio of width to height. The tool shows both.

## Related tools

- [Image Resizer](https://uttir.com/image-resizer) — Resize images to exact pixel dimensions with optional aspect-ratio lock.
- [Image Cropper](https://uttir.com/image-cropper) — Crop a precise pixel region from any image.
- [Image Compressor](https://uttir.com/image-compressor) — Shrink image file size with quality and format control, and see the savings before you download.

---

For the full HTML page with the live tool, visit https://uttir.com/aspect-ratio-calculator.
This file is the markdown rendering at https://uttir.com/aspect-ratio-calculator.md. See https://uttir.com/llms.txt for a site-wide summary.