ConvertFast

Resize Video

Change video dimensions for social platforms and websites.

Upload Video

Drop video hereChoose VideoUp to 100MB • MP4, MOV, WEBM, AVI
No signup•Secure processing•Auto-deleted after processing

Supported Input and Output

Accepted input
MP4, MOV, AVI, MKV, and WebM video
Output
MP4 video at custom pixel dimensions
Upload limit
Up to 100 MB per video
Controls
Custom width and height, Keep-aspect-ratio option

What This Processing Changes

Resizing changes frame dimensions and re-encodes the video. Disabling aspect-ratio preservation can stretch or squash the picture.

How to Check the Result

  1. Read frame dimensions in the downloaded file.
  2. Check geometry; disabling aspect ratio intentionally stretches this landscape sample.

Limits and Troubleshooting

  • Keep aspect ratio enabled unless the destination requires exact dimensions.
  • Use even-numbered dimensions for the broadest codec compatibility.

How Video Resizing Works

  • Custom Width & Height: Set custom target width or height in pixels to fit specific website or app container requirements.
  • Aspect Ratio Lock: Keep aspect ratio enabled to prevent stretching, distortion, or unnatural letterboxing.
  • Social Media Formatting: Resize video dimensions for Instagram, TikTok, YouTube Shorts, or web banner placements.

Frequently Asked Questions

How do I resize video dimensions online?

Upload your video file, enter custom target width or height (or select a standard percentage preset), and click process to generate your resized video.

Can I maintain the original aspect ratio while resizing?

Yes, preserving aspect ratio automatically calculates the corresponding width or height to prevent image stretching or distortion.

Does resizing video dimensions reduce file size?

Reducing width and height decreases frame area, which generally lowers file size when re-encoded at appropriate bitrates.

Which formats are supported for video resizing?

ConvertFast supports resizing common web formats including MP4, MOV, WEBM, AVI, and MKV.

Related Video Resolution Tools

Change Video ResolutionCustom Resolution Output
Convert Video To 720p720p HD Preset
Convert Video To 1080p1080p Full HD Preset
Compress VideoShrink Video File Size
Resize VideoWidth & Height Dimensions
Reduce Video SizeTarget File Reduction

Worked Example: Fit a landscape clip inside a 320 × 320 box.

  1. Upload sample.mp4 from the example below.
  2. Set width: 320, height: 320, Keep aspect ratio: on.
  3. Process and download; play the result from beginning to end.

Check Your Download

  • Read frame dimensions in the downloaded file.
  • Check geometry; disabling aspect ratio intentionally stretches this landscape sample.

Limit: Pixel dimensions are not a guaranteed file-size limit. Use Compress Video for requirements measured in MB.

Download the example input and repeat the steps above. These are generated test files, not customer uploads.

Input bytes
135,582
Output bytes
50,327
Verified result
320 × 180; 2.020 seconds; h264
Test date
2026-10-06

Measurements apply to this sample and these settings. Other inputs and codec versions can produce different sizes and results.