Why does the output width sometimes change when I set a target height?

The tool preserves the original aspect ratio. If your source is 16:9 and you target 1080p height, the width is calculated as 1920. If you target a platform with a different ratio (e.g. 1:1 for Instagram), the tool adds letterbox/pillarbox padding to fit without cropping.

What does "odd dimension" mean and why does it matter?

Most video codecs (H.264, H.265) require both width and height to be divisible by 2. If the calculated dimension is odd, FFmpeg will error. The tool automatically rounds up to the nearest even number and flags this.

Can I use this to upscale a video?

Yes, but upscaling increases file size without adding real detail. It is generally better to keep the original resolution and let the player or platform scale up on display.

Do I need to install anything to use this tool?

No. The calculator runs entirely in your browser. To actually resize a video, you will need FFmpeg or HandBrake installed on your computer — the tool provides the exact command to run.

Why are the bitrate recommendations different for each platform?

Each platform has its own recommended upload bitrate. Higher resolutions need more data per frame to maintain quality. The recommendations follow common platform guidelines (YouTube, Vimeo, Twitter) and general encoding best practices.

Video Resizer

Name: Video Resizer
Availability: InStock
Author: Nham Vu

Enter your video dimensions and target platform to get the correct output size, bitrate recommendations, and FFmpeg command to resize it.

Source Video Dimensions

Width (px)

Height (px)

Detected aspect ratio: 16:9

Target Platform / Preset

Fit Mode

Letterbox / pillarbox to fit inside target without cropping.

Enter source dimensions and press Calculate Resize

Output Dimensions

Source

3840 × 2160

16:9

Output

1920 × 1080

16:9

Aspect Ratio Preview

Source

Output

Recommended Bitrates

Video (H.264)

5 Mbps

Video (H.265)

2.5 Mbps

Audio (AAC)

192 kbps

FFmpeg Command

HandBrake CLI Command

Copied!

Summary

Enter your video dimensions and target platform to get the correct output size, bitrate recommendations, and FFmpeg command to resize it.

How it works

Enter the width and height of your original video (e.g. 3840 x 2160).
Choose a target platform preset or enter a custom target width or height.
The calculator preserves the original aspect ratio and shows the exact output dimensions.
Review the recommended video bitrate, audio bitrate, and codec for the target resolution.
Copy the generated FFmpeg or HandBrake CLI command and run it in your terminal.

Use cases

Resize a 4K recording down to 1080p before uploading to YouTube.
Scale a vertical phone video (9:16) to the correct size for Instagram Reels.
Check what resolution a widescreen 21:9 source becomes at 1080p height.
Prepare a video for Twitter/X, TikTok, LinkedIn, or Facebook with correct dimensions.
Get a precise FFmpeg scale filter command without guessing dimensions by hand.
Verify output dimensions before a long encode to avoid wasting time.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu