Aspect Ratio Calculator

How to use?

With Calculate ratio mode, just enter width and height and you get the simplified aspect ratio back. In Calculate dimension mode, you give it the ratio (16:9, for instance) plus one side, and it works out the other.

Aspect ratio: width to height

The aspect ratio is the proportion between an image's width and height, written as W:H. Common standards are 4:3 (CRT TVs and computer monitors until the early 2000s), 16:9 (HD, Full HD and 4K — adopted by SMPTE in 1990 and dominant since the smartphone era), 21:9 (ultrawide, used in cinema and gaming monitors), 1:1 (classic Instagram posts) and 9:16 (vertical video for Reels and TikTok). To convert a known height to width at a target ratio, multiply: width = height · (W/H); the inverse gives the height. Letterboxing (black bars) appears when content with one ratio is displayed on a screen with another — for example 16:9 video on a 4:3 screen. Note also the distinction between display aspect ratio and pixel aspect ratio: some legacy formats (PAL/NTSC anamorphic DVD) used non-square pixels, so a 720×576 frame still rendered as 4:3 or 16:9.

Applications: web, video and photography

Used in responsive web design (CSS aspect-ratio: 16/9 reserves space for images and embeds), video editing (Premiere, Final Cut, DaVinci Resolve sequence settings), digital photography (sensor crop modes), broadcast standards and ultrawide monitor setups for programmers, traders and content creators.

FAQ

How do I scale an image without distortion? Keep the ratio constant. If you know the new width, compute height = width · (H/W) using the original ratio.

What is the difference between 16:9 and 16:10? 16:10 (1.6) is slightly taller than 16:9 (1.78). It was common on laptop screens between 2003 and 2010 and is returning on some premium notebooks.

Why does my 16:9 video show black bars on YouTube? Usually because the encoded resolution does not match true 16:9, or the player is on a non-16:9 viewport — the black bars preserve the original ratio.