Aspect Ratio Calculator
Resize dimensions without distortion, turn any width × height into a clean ratio, and grab the exact pixel size for any platform, instantly, in your browser.
Common ratios
One-tap size presets
Social media
Video & display
Photo & print
What is an aspect ratio?
An aspect ratio is the proportional relationship between width and height,
written as width:height.
A 16:9 image is 16 units wide for every 9 units tall, and that proportion holds at any
size, which is why 1280 × 720 and 1920 × 1080 look identical in shape. Matching the right
ratio is what keeps photos and videos from being stretched, squished, or awkwardly cropped.
How do I calculate an aspect ratio?
To reduce any dimensions to their simplest ratio, divide both numbers by their greatest common divisor (GCD):
GCD(1920, 1080) = 120
1920 ÷ 120 = 16
1080 ÷ 120 = 9
→ 1920 × 1080 = 16:9
To resize while keeping the ratio, multiply by the scale factor instead:
new height = (original height ÷ original width) × new width.
The calculator handles both, switch tabs for whichever you need.
Common aspect ratios
| Ratio | Where it's used | Example size |
|---|---|---|
| 16:9 | YouTube, modern TVs, most monitors | 1920 × 1080, 3840 × 2160 |
| 9:16 | TikTok, Reels, YouTube Shorts, Stories | 1080 × 1920 |
| 1:1 | Instagram square posts, profile pictures | 1080 × 1080 |
| 4:5 | Instagram portrait posts | 1080 × 1350 |
| 4:3 | Older displays, many cameras, iPad | 2048 × 1536 |
| 3:2 | 35mm photography, DSLRs | 3000 × 2000 |
| 21:9 | Ultrawide monitors, cinematic video | 3440 × 1440 |
| 1.91:1 | Facebook / LinkedIn link previews | 1200 × 630 |
Popular image sizes
All sizes →Browse by ratio
All ratios →Frequently asked questions
What is an aspect ratio? +
An aspect ratio describes the proportional relationship between an image or screen’s width and height, written as width:height (for example 16:9). It stays the same no matter the resolution, 1280 × 720 and 1920 × 1080 are both 16:9.
How do I calculate aspect ratio? +
Divide both the width and height by their greatest common divisor (GCD). For 1920 × 1080, the GCD is 120, so 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9, giving 16:9. The calculator above does this instantly, just switch to the “Get the ratio” tab.
What is the aspect ratio of 1920 × 1080? +
It is 16:9, the standard widescreen ratio used by Full HD video, YouTube, and most monitors and TVs.
How do I resize an image without distorting it? +
Keep the aspect ratio constant. Enter your original width and height, turn on “Lock aspect ratio,” then change either the new width or height, the other value updates automatically so the image scales without stretching.
What aspect ratio should I use for YouTube, Instagram, and TikTok? +
YouTube videos and thumbnails use 16:9 (1280 × 720 thumbnails). Instagram square posts are 1:1 (1080 × 1080) and portrait posts are 4:5 (1080 × 1350). TikTok, Reels, and Stories are vertical 9:16 (1080 × 1920). Use the one-tap presets above to fill these in.
Is AspectKit free, and are my images uploaded? +
AspectKit is completely free, with no sign-up. Every calculation runs entirely in your browser, nothing is uploaded or stored.