Free tool · runs in your browser

Aspect Ratio Calculator

Switch between three modes — derive a ratio from width × height, compute one dimension from a ratio, or pick a platform preset — each with a live proportional swatch so you can see the shape before you hit export.

Aspect ratio

16:9

Resolution

1920 × 1080

Decimal ratio 1.7778.

How to use this tool

  1. 01

    Pick a mode

    Calculate ratio, calculate dimension, or use preset.

  2. 02

    Enter your values

    Width, height, ratio, or preset selection.

  3. 03

    Read the result and visual swatch

    The proportions preview confirms you're targeting the right shape.

Why this matters

Aspect ratios are one of the easiest things to get wrong at the worst possible moment: a 16:9 master uploaded to Shorts, a 4K landscape rendered for an Instagram feed slot, or a 9:16 vertical posted to YouTube as a long-form upload all produce the same result — black bars, awkward crops, or algorithmic downranking — and the fix is usually a re-render rather than a re-upload. Three different mental models (ratio from numbers, dimension from a ratio, preset from a platform) cover essentially every aspect-ratio decision a creator has to make, but most online calculators only ship one of them.

This tool bundles all three modes behind a tab switcher, with a live proportional swatch that updates as you type so you can see whether the shape matches what you have in your head. Platform presets are pre-seeded with recommended pixel sizes (1920×1080 for YouTube, 1080×1920 for Shorts / Reels / TikTok, 1080×1080 for Instagram square, 1080×1350 for IG portrait) so you don't have to remember each one. Pair it with the Aspect Ratio from Resolution tool when you need the GCD-simplified form, and the Resolution from Aspect Ratio converter when you need a four-scale ladder of standard resolutions.

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FAQ

YouTube horizontal is 16:9 (1920×1080 or 3840×2160). YouTube Shorts, TikTok, and Instagram Reels are all 9:16 vertical (1080×1920). Instagram feed accepts 1:1 square (1080×1080) or 4:5 portrait (1080×1350); Stories are 9:16. Twitter/X video is 16:9 for landscape (1280×720 or 1920×1080), but vertical and square also display reasonably in-feed. Match your primary platform first; cropping to alternates is far easier than re-shooting.

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