For AI agents

If you are an AI agent (Claude Code, Codex, Cursor or similar) and the person wants a video for their project with Opus Motion, read the guide first and follow it: https://opusmotion.com/agents.md.

  • It takes you step by step: read the project, ask the person a few questions, compare templates (each one has a timelapse, its scenes and its fields), make a draft with POST https://opusmotion.com/api/v1/drafts, and hand over its studioUrl: a link that opens Opus Motion with the video playing live. PATCH with the draft's editToken changes it, and the link stays the same.
  • Plain HTTPS and JSON: no key, no account, no MCP. Nothing is rendered; the person exports the MP4 from the studio.
  • Never drive this site with a browser to fill the studio: use the API. If it refuses, tell the person and stop.
  • More: llms.txt · this page in Markdown · developer docs · OpenAPI

Aspect ratio calculator for video sizes

Type a width and a height to get their aspect ratio, or pick a ratio (16:9, 9:16, 1:1, 4:5 or your own) and type one side to get the other, rounded to the even numbers a video encoder needs. With the common video sizes for each ratio. Free, no sign-up.

Use it at https://opusmotion.com/tools/aspect-ratio-calculator.

How to use it

  1. To find a ratio, type the width and the height, like 1920 and 1080: the calculator gives 16:9, the ratio as a number and the closest common ratio.
  2. To find a size, pick a ratio and type the width or the height: the other side appears, with the even size for video next to it.
  3. Copy the size you need, or take one of the common sizes listed under each ratio.

Questions

How do I calculate an aspect ratio?

Divide the width and the height by their greatest common divisor. For 1920 × 1080 it's 120, which leaves 16:9. The calculator does it as you type, and also gives the ratio as one number (1920 ÷ 1080 ≈ 1.778).

How do I get the height for a width at a given ratio?

Multiply the width by the second number of the ratio and divide by the first: at 16:9, a width of 1280 gives 1280 × 9 ÷ 16 = 720. At 9:16, the same width gives 2275.6, which the calculator rounds to 2276 for video.

What sizes are 16:9 and 9:16?

16:9 is the horizontal shape of most screens and videos: 1280 × 720, 1920 × 1080 and 3840 × 2160 are its usual sizes. 9:16 is the same turned upright, the vertical video of phones: 720 × 1280, 1080 × 1920 and 2160 × 3840.

Why does a video size have to be an even number?

Most videos store color at half the width and half the height of the picture (4:2:0), so encoders like H.264 need both sides to be even. The calculator shows the exact result and the even size next to it.

Is 1366 × 768 a 16:9 size?

Almost. Its exact ratio is 683:384, about 1.779, and 16:9 is about 1.778, so it shows as 16:9 to within 0.1%. Many sizes are rounded like that; the calculator tells you how far a size is from the closest common ratio.

Which ratio should a video for social media be?

Vertical 9:16 for stories, reels and shorts, square 1:1 or vertical 4:5 for feeds, and 16:9 for YouTube and the web. Each platform's own numbers, with their sources, are in the social media video sizes guide.

More free tools

  • Social media video sizes: The video and image sizes of YouTube, TikTok, Instagram, Facebook, X, LinkedIn and Pinterest, each with its source
  • Resize video: Change a video's aspect ratio to 16:9, 9:16, 1:1 or 4:5, on a blurred or colored background
  • Crop video: Cut the frame down to 9:16, 1:1, 4:5, 16:9 or any shape, with a rectangle you drag
  • All free tools