What does this tool do?
The Aspect Ratio calculator instantly derives the aspect ratio (e.g. 16:9 for 1920×1080), its decimal equivalent, and the padding-top percentage from a width and height. It saves time for designers, video editors, and anyone building responsive layouts.
How to use it
- Enter your values into the fields.
- The result is calculated instantly.
- Read or copy the result.
Ratio, decimal, and padding-top at a glance
Enter the width and height in pixels and the tool simplifies the ratio by finding the greatest common divisor (1920×1080 → 16:9), shows the decimal value (1.7778), and the padding-top percentage used in CSS (56.25%). Preset buttons cover common ratios like 16:9, 4:3, 1:1, 21:9, 3:2, and 9:16. A small visual preview also helps you picture the proportions at a glance.
Find dimensions with the scale calculator
Use the scale calculator to lock one side and find the other proportionally. For example, with a 16:9 ratio, entering a new width of 1280 computes a height of 720; or enter a height to get the matching width. This is ideal for resizing an image or video without distorting its aspect ratio, ensuring it scales cleanly to any target size.
Frequently asked questions
What is the padding-top percentage for?
It's used in responsive CSS to keep a box at a fixed aspect ratio. Applying padding-top: 56.25% to a container holds a 16:9 shape no matter the box width (the classic 'intrinsic ratio' technique).
How is the ratio simplified?
The tool finds the greatest common divisor (GCD) of the entered width and height to reduce the ratio to its simplest form. For example, the GCD of 1920 and 1080 is 120, so the result displays as 16:9.
What does the decimal value (e.g. 1.7778) mean?
It's the width divided by the height, the numeric form of the ratio. 16:9 ≈ 1.7778, 4:3 ≈ 1.3333, 1:1 = 1. This value is handy for quickly comparing ratios.
Is Aspect Ratio Calculator free?
Yes. Aspect Ratio Calculator and all 300+ tools on MagmaNex are completely free with no signup or account required.
Is my data safe?
Yes. Everything runs locally in your browser. The data you enter is never sent to a server, stored, or shared.
Does it work on mobile?
Yes. Aspect Ratio Calculator works on phones, tablets and desktops — no app download needed.
🔒 Privacy: everything runs in your browser, your data is never sent to a server.