Aspect Ratio Calculator
Calculate aspect ratios, find missing dimensions, and resize while keeping proportions. Perfect for video and web.
Enter dimensions to calculate the aspect ratio
How to Use
Enter dimensions
Type a width and height in pixels (or any unit). The aspect ratio is calculated instantly.
Find a missing dimension
Switch to the second mode, enter the ratio and one dimension to calculate the other proportionally.
Compare to common ratios
The tool shows the nearest common aspect ratios (16:9, 4:3, 1:1, etc.) for reference.
FAQ
An aspect ratio describes the proportional relationship between an image's width and height. It is written as W:H (e.g., 16:9) or as a decimal (e.g., 1.78). The same aspect ratio can apply to any resolution, from 1280×720 to 3840×2160 — both are 16:9.
16:9 — widescreen HD/4K video and monitors. 4:3 — older TVs and displays. 1:1 — square (Instagram). 21:9 — ultrawide monitors. 9:16 — vertical video (Reels, TikTok). 3:2 — DSLR / mirrorless camera sensors.
Enter your original dimensions to find the ratio, then switch to "From ratio + one side" mode and enter the new width or height. The tool calculates the other dimension automatically.
The golden ratio is approximately 1.618:1 (or 1:0.618). It is considered aesthetically pleasing and appears frequently in art, architecture, and nature. The ratio is φ (phi) ≈ 1.6180339887.