Aspect Ratio Calculator
Compute the matching dimension for a target aspect ratio. Includes presets for 16:9 / 4:3 / 21:9 / 1:1 / 9:16.
×
16:9
Common Resolution Presets
| Name | Width | Height | Ratio |
|---|
Popular uses
Calculate 16:9 and 9:16 sizesPlan social resolutionsAvoid bars and padding
What this tool does
- Width ↔ height calculator
- Common-ratio presets
- Even-number correction for H.264
How to use
- 1
Pick a ratio
Preset or custom.
- 2
Enter width or height
The other side calculates automatically.
- 3
Copy the result
Paste straight into ffmpeg.
What each setting means
Aspect ratio
Width:height ratio (e.g. 16:9).
Width / Height
One drives the other.
Recommended settings
YouTube / TV
16:9 (1920×1080)
Global standard.
TikTok / Reels / Shorts
9:16 (1080×1920)
Vertical SNS standard.
Cinematic
21:9 (2560×1080)
Cinemascope-like framing.
Common pitfalls
Symptom: H.264 encode fails
Cause: Odd resolution.
Fix: Use scale=-2:720 to force even.
Equivalent FFmpeg commands
Reference commands you can run on the desktop FFmpeg CLI.
Keep width, set height to 720
ffmpeg -i input.mp4 -vf scale=-2:720 -c:v libx264 -crf 23 output.mp4Force exact resolution
ffmpeg -i input.mp4 -vf scale=1280:720,setsar=1:1 output.mp4Browser support & limits
- Calculator only — apply via another tool.
Privacy
This tool only does math in your browser. Inputs stay on your device — nothing is uploaded. Read the privacy policy →
Frequently asked questions
Why even resolution?
H.264 / H.265 use 4:2:0 chroma subsampling, which requires even dimensions.
21:9 vs 2.35:1?
Similar, not identical. 21:9 ≈ 2.33:1; 2.35:1 is true cinemascope.