Aspect Ratio Calculator
Calculate missing width or height to preserve any aspect ratio, with common presets built in.
About Aspect Ratio Calculator
An aspect ratio is the proportional relationship between a screen or image's width and height, written like 16:9 or 4:3. Keeping that ratio intact while changing one dimension is a constant problem for video editors, designers, and photographers who resize without wanting to distort their work or leave awkward letterbox bars.
The math is a simple proportion: the missing side equals the known side multiplied by the target ratio factor. For a 16:9 frame at 1920 wide, height = 1920 × 9 ÷ 16 = 1080. Because pixels must be whole numbers, results round to the nearest integer, which is negligible at typical image sizes. Built-in presets cover the common ratios, and custom values handle anything else.
Video editors size frames for YouTube and social posts, web designers fit images into responsive layouts, and photographers prepare prints without cropping out subjects. Anyone who resizes images or video for a specific platform needs the target ratio before they export, which makes this a pre-production staple.
How to Use
- Enter one dimension (width or height).
- Pick a preset like 16:9 or enter a custom ratio.
- Read the matching dimension instantly.
Example
16:9 ratio, width 1920 Height: 1080
1920 ÷ 16 × 9 = 1080, so a 16:9 video at 1920 wide is exactly 1080 high.
FAQ
What is an aspect ratio?
The proportional relationship between width and height, written like 16:9 or 4:3.
Which presets are included?
16:9, 4:3, 1:1, 3:2, 21:9, and 9:16, with custom ratios for anything else.
Why do my image dimensions keep getting rounded?
Pixels must be whole numbers, so results round to the nearest integer, which is negligible for large images.
What is the aspect ratio of a typical smartphone screen?
Most modern phones use 19.5:9 or 20:9, taller than the 16:9 of most TVs and older phones. Tall ratios let a display fill the hand while remaining easy to grip and scroll.
How do I crop an image to a specific aspect ratio?
First compute the matching dimension with this tool, then set the crop rectangle to those proportions in any image editor. Working from the ratio, not guesswork, prevents distorted or unexpectedly tight crops.