100% Free

Aspect Ratio
Calculator

Enter any width and height to find the exact ratio — or scale your dimensions while keeping proportions perfectly locked. Includes presets for every major platform.

Quick platform presets
A
Find Ratio from Dimensions
Enter width & height → get ratio
Width (px)
×
Height (px)
Simplified Ratio
—
Decimal (W÷H)
—
B
Scale to New Dimensions
Lock a ratio → find the missing side
Aspect Ratio
:
Enter ratio above to lock
Calculate
Calculated Height
—
Visual Preview
Enter dimensions above
Common Ratios — click to load into Calculator B
Quick reference
Guide & Reference

Everything you need to know
about aspect ratios

Whether you're a video editor, designer, photographer, or developer — understanding aspect ratios saves you from stretched images, black bars, and rejected uploads.

📋
How to Use This Tool
  1. Calculator A — Type any width and height. The simplified ratio and decimal appear instantly.
  2. Calculator B — Enter a ratio (e.g. 16:9), then type one known dimension. The missing side is calculated automatically.
  3. Presets — Tap any platform badge to load its standard ratio into both calculators at once.
  4. Common Ratios grid — Click any cell to load that ratio into Calculator B instantly.
  5. Use the copy buttons to grab any result to your clipboard with one tap.
  6. The visual preview animates in real time to show the exact shape of your ratio.
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When You Need It
  • Resizing a YouTube thumbnail without distortion (1280×720 to 2560×1440)
  • Cropping photos to 4:5 portrait for the Instagram feed
  • Calculating the height of a 16:9 banner given a fixed width
  • Checking whether an imported video asset matches your timeline settings
  • Scaling a print design from A4 to A3 while keeping layout intact
  • Finding black bar dimensions for letterboxing or pillarboxing
  • Setting canvas size in Figma, Photoshop, or Premiere to exact platform specs
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Frequently Asked Questions
What exactly is an aspect ratio?
An aspect ratio describes the proportional relationship between width and height — written as W:H. A 1920×1080 frame and a 1280×720 frame both share the same 16:9 ratio because their proportions are identical, even though their pixel counts differ.
Why does my ratio show a decimal like 1.91:1?
Some ratios (like Instagram's landscape spec at 1080×566) don't reduce to clean integers. This tool shows the mathematically correct simplified form. For whole-number ratios like 16:9 or 4:3, the result is always integers.
Will the calculated height always be a whole pixel?
Pixels must be whole numbers, so when the math produces a decimal, this tool rounds to the nearest integer. The rounding error is always less than 1 pixel — completely negligible for any real-world use.
What's the best aspect ratio for YouTube?
YouTube recommends 16:9 for all videos. For thumbnails, upload at 1280×720 px (minimum) or 1920×1080 px for sharper display on retina screens. Use the YouTube preset above to load these settings instantly.
What ratio should I use for Instagram?
It depends on your post type. Square feed posts use 1:1, portrait feed posts use 4:5 (fills the most screen space), landscape feed posts use 1.91:1, and Stories or Reels use 9:16. All presets are available above.
Is my data sent to any server?
No. Every calculation runs entirely in your browser using JavaScript. No dimensions, no results, and no usage data are transmitted to any server. The tool works fully offline once the page has loaded.