Image & Video Aspect Ratio Calculator
Calculate standard aspect ratios (16:9, 4:3, 21:9), resize dimensions with video-safe rounding, find matching resolutions, and preview your aspect ratio on a real-time proportional canvas.
Input Dimensions (Pixels)
Calculation Results
LandscapeReal-Time Visual Canvas Preview
Developer Code Snippets
Instant Copyaspect-ratio: 16 / 9;aspect-videoffmpeg -i in.mp4 -vf "scale=1920:1080" out.mp4Complete Aspect Ratio Reference & Guide
Comprehensive explanation of display aspect ratios, video codecs, and responsive design guidelines.
16:9 Standard Widescreen
16:9 is the international standard format for HDTV, Full HD (1920×1080), 4K UHD (3840×2160), YouTube, and computer displays. It replaced 4:3 as the universal compromise between classic cinema and television.
9:16 Vertical Revolution
9:16 is the exact inverse of 16:9, tailor-made for vertical smartphone orientation. It is the dominant format for TikTok, Instagram Reels, YouTube Shorts, and Snapchat stories, designed for one-handed thumb scrolling.
21:9 & Cinematic Ultrawide
21:9 (technically 64:27 or 43:18) offers ultra-panoramic field of view for curved gaming monitors and theatrical film productions. Movies shot in Anamorphic 2.39:1 fill 21:9 screens without black letterbox bars.
Frequently Asked Questions (FAQ)
How is an aspect ratio calculated mathematically?
Aspect ratio is calculated by finding the Greatest Common Divisor (GCD) of width and height using the Euclidean algorithm, then dividing both dimensions by the GCD. For example, for 1920 × 1080, the GCD is 120: 1920 ÷ 120 = 16, and 1080 ÷ 120 = 9, yielding 16:9.
Why do video encoders require even numbers (Mod 2 / Mod 4)?
Video codecs like H.264 (MP4) and H.265 rely on YUV 4:2:0 chroma subsampling. Chroma pixels are shared across a 2×2 block of luma pixels. If either dimension has an odd number of pixels, the video cannot be divided evenly into macroblocks, causing encoding errors or playback glitching.
What is the difference between DAR, SAR, and PAR?
DAR (Display Aspect Ratio) is the physical proportion shown on the screen (e.g. 16:9). SAR (Storage Aspect Ratio) is the raw pixel resolution ratio (e.g. 720×480 on DVD). PAR (Pixel Aspect Ratio) is the shape of an individual pixel (square vs anamorphic rectangular pixels).