Aspect Ratio Calculator — FAQ
Common questions about how to use the free online aspect ratio calculator.
How does the aspect ratio calculator work?
Enter an aspect ratio (like 16:9) and one dimension — width or height — and the tool instantly computes the other so the proportion stays exactly locked. Change either value and the other updates automatically. You can also enter a width and height to simplify them to their reduced ratio.
Is the aspect ratio calculator free?
Completely free. No sign-up, no downloads, no limits — use it as many times as you like.
What is an aspect ratio?
An aspect ratio is the proportional relationship between a rectangle's width and height, written as W:H (for example 16:9). It describes shape, not size — a 1920×1080 image and a 320×180 thumbnail share the same 16:9 ratio.
How do I find a missing dimension from a ratio?
Select or type the aspect ratio (e.g. 16:9), then enter the dimension you know — width or height. The tool computes the other dimension instantly using the formula: height = width × ratioH / ratioW (or width = height × ratioW / ratioH).
Can it simplify a resolution to a ratio?
Yes. Switch to the Simplify Ratio tab, enter your width and height (like 1920 and 1080), and the tool reduces them to the simplest whole-number ratio (16:9) along with the decimal equivalent.
Which ratio presets are included?
The presets cover the most common formats: 16:9 (widescreen HD/4K), 4:3 (standard SD and presentations), 21:9 (ultrawide/cinematic), 1:1 (square, used by Instagram), 3:2 (DSLR sensors and 35mm film), and 9:16 (vertical/portrait for phones and Reels). You can also type any custom ratio.
What if the computed dimension is not a whole number?
The tool shows the exact decimal result and flags it with a warning when the computed dimension is not a whole pixel (for example, 16:9 + width 1000 gives height 562.5). You can then round up or down as suits your use case.
Why does keeping the aspect ratio matter?
Maintaining the aspect ratio prevents images, videos, and layouts from stretching or squashing. Changing only one dimension without scaling the other distorts the content, making subjects look too wide, too tall, or otherwise unnatural.
Is my data stored or sent anywhere?
No. All calculations run entirely in your browser. Nothing you enter is stored, logged, or sent to any server.
Does it work on mobile?
Yes, the tool is fully responsive. Inputs, presets, and the preview all fit on small screens without horizontal scrolling.