This free aspect ratio calculator does two things: it scales a width or height to a target ratio like 16:9, 9:16 or 21:9, and it works out the simplified aspect ratio of any resolution. Handy for setting up stream canvases and browser sources, exporting the right size for YouTube, Shorts, TikTok or Reels, and keeping thumbnails and overlays proportional.
Common streaming ratios
16:9 is standard for Twitch, YouTube and most horizontal video (1920×1080, 2560×1440). 9:16 is vertical for TikTok, Shorts, Reels and Kick vertical (1080×1920). 21:9 is ultrawide, 4:3 and 1:1 show up in retro and square formats. Pick a preset and type one dimension to get the matching one.
Frequently asked questions
How do I calculate an aspect ratio?
Divide the width by the height and simplify. This tool does it for you — enter a resolution in the second box to see its simplified ratio, or pick a ratio and a known dimension to get the other.
What is 16:9 in pixels?
Common 16:9 resolutions are 1280×720, 1920×1080 (1080p), 2560×1440 (1440p) and 3840×2160 (4K).
What ratio should a vertical stream be?
9:16, typically 1080×1920 — the standard for TikTok, YouTube Shorts, Reels and vertical Kick streams.
Is it free?
Yes, completely free and it runs entirely in your browser.
More free tools for streamers
Browse the full free tools hub — including an OBS bitrate calculator and a Twitch emote resizer.
Last updated: July 2026