Aspect Ratio Calculator

Common Aspect Ratios Explained

An aspect ratio describes the proportional relationship between a display or image's width and height. It is written as two numbers separated by a colon (e.g., 16:9). The first number is always the width and the second is the height.

16:9 – Widescreen Standard

The dominant ratio for modern HD and 4K displays, laptops, HDTVs, YouTube videos, and presentations. A 1920×1080 or 3840×2160 (4K) display is 16:9. Most video content is produced in this ratio.

4:3 – Legacy Standard

The original format for television and computer monitors before widescreen became common. Still used for some printed photographs and older educational projectors.

1:1 – Square

Used for profile pictures, thumbnails, and Instagram posts. DSLR and medium format cameras can often produce square crops.

9:16 – Vertical / Portrait

The format for mobile phone screens and short-form vertical video (TikTok, Instagram Reels, YouTube Shorts).

21:9 – Ultrawide

Used on ultrawide monitors for gaming and productivity, and increasingly used for cinematic film releases to give a wide letterbox appearance.

3:2 – Photography Standard

The format produced by most DSLR and mirrorless cameras using a full-frame or APS-C sensor. A 3:2 image is slightly wider than 4:3 but narrower than 16:9.

How to Maintain Aspect Ratio When Resizing

To resize an image without distorting it, keep the ratio of width to height constant. If you know one new dimension, multiply by the ratio to find the other:

• New height = New width ÷ (Original width ÷ Original height)
• New width = New height × (Original width ÷ Original height)

For resizing actual image files, use our PNG resizer, JPG resizer, or canvas resizer to scale images to exact pixel dimensions.

Frequently Asked Questions

What aspect ratio should I use for YouTube thumbnails?

YouTube recommends a 16:9 aspect ratio for thumbnails, at a resolution of 1280×720 pixels (minimum) up to 1920×1080 pixels. Use our YouTube thumbnail size guide for all the exact dimensions.

Why are ratios expressed in their simplest form?

Simplifying ratios (by dividing both numbers by their GCD) makes them easier to read and compare. For example, 1920:1080 simplifies to 16:9, which is more recognizable and communicates the proportional relationship more clearly.

What is the difference between aspect ratio and resolution?

Resolution refers to the actual number of pixels (e.g., 1920×1080). Aspect ratio is the proportional relationship between those numbers (16:9). Two images can have the same aspect ratio but very different resolutions.