Aspect Ratio Calculator
Enter any width and height to find the simplified aspect ratio, or use a known ratio to scale to a target dimension. Handy for resizing images, designing thumbnails, or fitting video to a screen without distortion.
Common ratios
How to use
- To find a ratio: enter the width and height and get the simplified ratio like 16:9.
- To scale: switch to the scale tab, enter a target width or height and it calculates the other dimension.
- Click any of the common ratio presets to fill in the fields quickly.
Related tools:
Aspect ratio is the proportional relationship between width and height. 16:9 is widescreen (most monitors and TV screens). 4:3 is older squarish screens and tablets. 1:1 is square (Instagram posts). The ratio stays constant when you scale up or down - a 1920x1080 screen and a 3840x2160 (4K) screen are both 16:9.
The most common use is resizing media while keeping proportions. If you have a 1200x800 image and need to scale it to 900px wide, what should the height be? 900/1200 x 800 = 600px. The calculator handles this in both directions and also identifies the nearest named ratio for any custom dimensions.
Frequently Asked Questions
What is the 16:9 aspect ratio in common resolutions?
16:9 resolutions include 1280x720 (HD), 1920x1080 (Full HD), 2560x1440 (2K/QHD), 3840x2160 (4K UHD), and 7680x4320 (8K). All follow the same ratio - width is exactly 1.778 times the height.
How do I calculate a missing dimension from an aspect ratio?
For 16:9 with known width W: height = W x 9/16. With known height H: width = H x 16/9. For any ratio A:B with known width W: height = W x B/A.
Why do social media platforms have different required aspect ratios?
Each platform optimises for its display context. Instagram square (1:1) filled phone screens before landscape was supported. YouTube and most video uses 16:9 for widescreen TVs. Instagram Stories and TikTok use 9:16 (vertical phone screens). Knowing the required ratio before resizing prevents cropping surprises.