Aspect ratio is the proportional relationship between width and height. It is critical in web design, video production, and image editing to maintain correct proportions. Common ratios include 16:9 (widescreen), 4:3 (classic TV), 1:1 (square, Instagram), and 21:9 (ultrawide). This tool calculates aspect ratios from any dimensions and scales proportionally when you change width or height.
16:9
1.7778
1920x1080
Enter width and height values in pixels and the tool calculates the simplified aspect ratio instantly (e.g., 1920×1080 → 16:9). You can also enter an aspect ratio and one dimension to calculate the other - enter '16:9' with width 1920 and get height 1080. Common presets for standard ratios (16:9, 4:3, 1:1, 21:9, 9:16) are available. The tool also shows the ratio as a decimal value for CSS aspect-ratio property usage.
Aspect ratio calculation is used in responsive web design for maintaining image proportions, video player sizing, CSS aspect-ratio property values, calculating responsive iframe dimensions, creating properly sized social media images and ads, determining print dimensions from digital files, designing mobile app layouts for different screen ratios, and configuring video encoding settings with correct output dimensions.
The aspect ratio is calculated by dividing both width and height by their Greatest Common Divisor (GCD), computed using Euclid's algorithm: GCD(a, b) = GCD(b, a mod b) until b = 0. For example, GCD(1920, 1080) = 120, so 1920/120 : 1080/120 = 16:9. The decimal ratio (1.778 for 16:9) is useful for the CSS aspect-ratio property. Common screen ratios include 16:9 (1.778, HD/4K), 16:10 (1.6, MacBook), 4:3 (1.333, classic), 21:9 (2.333, ultrawide), and 1:1 (1.0, square).
An aspect ratio is the ratio of width to height, usually expressed as two numbers separated by a colon. 16:9 means the width is 16 units for every 9 units of height. A 1920×1080 display has a 16:9 aspect ratio.
Divide both width and height by their greatest common divisor (GCD). For 1920×1080: GCD is 120, so 1920/120 : 1080/120 = 16:9.
It depends on the context: 16:9 for hero images and video thumbnails, 4:3 for article images, 1:1 for profile pictures and product images, 2:3 or 4:5 for Pinterest and portrait content.
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