Aspect Ratio Calculator

Aspect ratios, explained

An aspect ratio describes the relationship between a frame’s width and its height, written as width:height. It does not fix the resolution — 1280×720 and 1920×1080 are different sizes but the same 16:9 shape. Getting the ratio right is what keeps your video filling the screen on its target platform without black bars or stretching.

The ratios you will actually use

• 16:9 — the standard for YouTube, desktop screens, and most screen recordings.
• 9:16 — vertical video for TikTok, Instagram Reels, and YouTube Shorts.
• 1:1 — square, popular for in-feed social posts.
• 4:3 — older displays, some slides and tablets.
• 21:9 — ultrawide and cinematic framing.

Resize without distortion

The golden rule of resizing is to scale width and height by the same factor. If you halve the width, halve the height. This calculator enforces that for you: lock a ratio, change one dimension, and the other follows so the proportions never break.

Converting between ratios

Moving footage between ratios — say 16:9 to 9:16 for a vertical cut — is not a pure resize; it is a re-frame. You either crop (lose part of the image) or pad (add bars). Decide which subject must stay in frame, then use the calculator to nail the exact target dimensions.

ScreenBuddy for Mac lets you export the same recording to multiple aspect ratios — 16:9, 1:1, and 9:16 — so one capture feeds every channel. See how it works.