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.