Aspect Ratio Calculator
Resize width or height without distorting the image.
Find the simplified aspect ratio of an image or video, and calculate a proportional new width or height so a resize never looks stretched or squashed.
How aspect ratio is calculated
An aspect ratio is the width compared to the height. To simplify it, divide both numbers by their greatest common divisor. For 1920 × 1080, the greatest common divisor is 120, so the ratio is 1920 ÷ 120 : 1080 ÷ 120 = 16:9.
To resize without stretching, keep the ratio the same:
- New height = new width × original height ÷ original width
- New width = new height × original width ÷ original height
Example: a 4000 × 3000 photo resized to 800 pixels wide becomes 800 × 3000 ÷ 4000 = 600 pixels tall.
Common aspect ratios
| Ratio | Common sizes | Used for |
|---|---|---|
| 16:9 | 1280 × 720, 1920 × 1080, 3840 × 2160 | HD and 4K video, YouTube, TVs, most monitors |
| 9:16 | 1080 × 1920 | Phone videos, Instagram Reels and Stories, TikTok, YouTube Shorts |
| 4:3 | 1024 × 768, 1600 × 1200 | iPads, older TVs, many phone photos |
| 3:2 | 6000 × 4000 | DSLR and mirrorless camera photos, 4 × 6 in prints |
| 1:1 | 1080 × 1080 | Square social media posts, profile pictures |
| 4:5 | 1080 × 1350 | Portrait Instagram posts |
"Ultrawide" monitors are often called 21:9, but common sizes like 2560 × 1080 actually simplify to 64:27 — close to, but not exactly, 21:9.
Tips
- Changing the ratio means cropping. Turning a 4:3 photo into 16:9 requires cutting some of the top or bottom — resizing alone will stretch it.
- Round to even numbers for video. Most video encoders need widths and heights divisible by 2, so 1279 × 720 may fail where 1280 × 720 works.
- Make images smaller, not bigger. Enlarging beyond the original size adds blur, not detail. After resizing, the image compressor can shrink the file further.
Frequently asked questions
How do I use this to resize an image or video?
Enter the original width and height, then type a new value into either the target width or target height field — the other one is calculated automatically to keep the same proportions.
What common ratios does this recognize?
It simplifies any dimensions down to their simplest ratio (like 1920×1080 → 16:9), and also lists a few common named ratios close to your input for reference.
What aspect ratio is 1080p?
1920 × 1080 (1080p) is 16:9, the standard widescreen ratio for HD video, YouTube and most TVs and monitors.