Aspect Ratio Calculator
Calculate pixel width or height for any aspect ratio including 4:3, 16:9, 21:9, and custom ratios.
Enter one dimension to get the other.
Enter an aspect ratio and one dimension — the other calculates instantly.
An aspect ratio is the proportional relationship between something’s width and its height, written as two numbers like 16:9. It describes the shape, not the size: a 16:9 frame is the same shape whether it’s a phone thumbnail or a cinema screen.
Common aspect ratios:
- 4:3, classic TVs and older monitors (1024×768, 1600×1200)
- 16:9, the widescreen standard (1920×1080, 3840×2160)
- 16:10, many laptop screens (1920×1200, 2560×1600)
- 21:9, ultrawide monitors (3440×1440)
- 1:1, square, used for Instagram posts
Finding a missing dimension: Given a ratio W:H and one side, the other follows:
- Height = Width × (H / W)
- Width = Height × (W / H)
So a 16:9 image 1920 pixels wide is 1920 × (9/16) = 1080 pixels tall.
The point people miss is that aspect ratio and resolution are different things. 1920×1080 and 3840×2160 are both 16:9, even though one packs four times the pixels. Resolution is how much detail you get; aspect ratio is only the shape.
It’s also why fitting a 16:9 video onto a 4:3 screen forces a choice: add black bars (letterboxing), crop the sides off, or stretch everyone into funhouse proportions. You can’t change the shape of a frame without either losing part of the image or padding it with bars.
How we build and check this converter
This converter runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.