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Aspect ratio calculator
Enter a width or a height, plus 16:9, 9:16, or a pasted 1920×1080. RatioFit returns the other side in whole pixels — for YouTube, Instagram, TikTok, and Reels.
Aspect ratio calculator
Width or height + a ratio. The other side fills in.
Ratio presets
Platform sizes
Pixel preview
How the math works
Aspect ratio is width compared to height. 16:9 means sixteen units wide for every nine tall. If you know the width, height = width × 9 ÷ 16. If you know the height, width = height × 16 ÷ 9. RatioFit rounds to the nearest pixel so encode settings stay integer.
You can type a colon ratio (16:9), a slash (9/16), a decimal (1.777), or a pixel pair (1920×1080). Pixel pairs set both fields and simplify the ratio. Swap flips the frame from landscape to vertical without retyping.
Common ratios
Open a dedicated calculator with typical pixel sizes already filled in.
Platform sizes
Recommended exports, not guesses from a screenshot.
FAQ
How do I use this aspect ratio calculator?
Pick a ratio (16:9, 9:16, 1:1, or type 1920×1080). Enter a width or a height — not both from scratch. RatioFit computes the missing side in whole pixels. The last field you type is the lock.
How do I calculate height from width and a ratio?
Height = width × (ratio height ÷ ratio width). For 16:9, height = width × 9 ÷ 16. A 1920-pixel width becomes 1080. For 9:16, height = width × 16 ÷ 9, so 1080 wide becomes 1920 tall.
How do I calculate width from height?
Width = height × (ratio width ÷ ratio height). A 1080-tall 16:9 frame is 1920 wide. A 1920-tall 9:16 frame is 1080 wide.
Can I paste 1920×1080 instead of 16:9?
Yes. The ratio field accepts 16:9, 16/9, 1.777, or a pixel pair like 1920×1080 or 1920x1080. Pixel pairs also fill both dimension fields.
What pixel size is 16:9?
Common 16:9 sizes are 1280×720 (720p), 1920×1080 (1080p), 2560×1440 (1440p), and 3840×2160 (4K). Any pair that simplifies to 16:9 is valid.