Aspect Ratio Calculator
Pick a ratio, enter one dimension, and get the exact pixel size for the other.
Aspect ratio
How GenMotion's free aspect ratio calculator works
Three steps, no account, and nothing to install.
- Step 1
Pick an aspect ratio
Start from a preset — 16:9, 9:16, 1:1, 4:5, 4:3 or 21:9 — covering every common video and social format.
- Step 2
Lock one dimension
Enter the width or height you already know and lock it. The calculator solves for the other side.
- Step 3
Read the exact pixels
Get the matching dimension instantly, ready to paste into your editor's export settings or a CSS rule.
Who is GenMotion's free aspect ratio calculator for?
Video editors
Work out a matching frame size when repurposing a landscape edit for vertical, without guessing at the crop.
Social media managers
Hit each platform's expected shape exactly, so nothing gets auto-cropped or recompressed on upload.
Front-end developers
Size a video embed or thumbnail container to a precise ratio and keep the layout from shifting.
Frequently asked questions
An aspect ratio is the proportional relationship between a frame's width and height — for example 16:9 (widescreen) or 9:16 (vertical). It determines the shape of your video regardless of its pixel size.
Multiply the width by the ratio's height and divide by its width. For 16:9 at 1920px wide: 1920 × 9 ÷ 16 = 1080px tall. This calculator does that for you — pick a ratio, lock one dimension, and read off the other.
Use 16:9 for YouTube and desktop, 9:16 for Reels, Shorts, Stories, and TikTok, 1:1 for square feed posts, and 4:5 for portrait feed posts. See our Social Video Size Guide for exact pixel sizes per platform.
Yes — it's completely free, runs entirely in your browser, and requires no sign-up.
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