Aspect Ratio Calculator
Calculate proportional dimensions for any aspect ratio (16:9, 4:3, 1:1, etc.)
Result:
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Lock an aspect ratio (16:9, 4:3, 21:9, 1:1, 9:16) and instantly compute the matching width or height when one dimension is fixed. Perfect for video thumbnails, banner sizing, photo crops and responsive embeds.
How to calculate aspect ratio
1
Pick a ratio
Choose from presets or set a custom ratio.
2
Enter one dimension
Type a width OR height — the other is calculated automatically.
3
Use the result
Copy the values and apply them to your design or video.
Common ratios
Quick presets for 16:9, 4:3, 21:9, 1:1, 3:2, 9:16 — or define your own.
Live recalc
Type a width or height and the other dimension updates instantly.
Custom ratio
Define any custom W:H ratio for non-standard formats.
Copy values
Copy width or height with one click.
FAQ
Aspect ratio is the proportional relationship between width and height — for example, 16:9 means width is 16 units for every 9 units of height.
16:9 is the standard for YouTube, TVs and modern displays. 9:16 is used for vertical video (TikTok, Reels).
1:1 (square) was the original Instagram format — it shows equally well on all devices and crops cleanly.
Pick 'Custom' and enter any W and H values. The calculator simplifies them automatically.
This tool calculates dimensions, not screen-diagonal inches. Use a separate display calculator for that.