Video Resolution Converter
Convert video between standard resolutions — 4K, 1080p, 720p, 480p, 360p — with the aspect ratio preserved.
Convert with this tool
or choose a file from your device — it is processed in this tab and never uploaded
Accepted: MP4, MOV, MKV, WebM, AVI, M4V
Files stay on your device. There is no upload, no queue and no watermark, so a conversion works even with the network switched off after the page has loaded.
Supported formats & processing
| Accepted input | MP4, MOV, MKV, WebM, AVI, M4V |
|---|---|
| Produced output | MP4, WebM or MKV at the selected resolution |
| Processing | FFmpeg.wasm (video engine, downloaded on first use) |
| Upload required | No — the file is read locally and never transmitted |
How to use this tool
- Add the videoThe source resolution is reported where the container allows it.
- Choose the target tier1080p for most delivery, 720p for web and mobile, 480p when size is critical.
- Let the tool preserve the aspect ratioThe height is computed from your source's ratio and rounded to an even number.
- Set the qualityA lower CRF preserves more detail in the smaller frame.
- Convert and compare the sizesThe result card reports the output dimensions and the size change.
About this tool
Resolution conversion is about matching the file to the screen it will be watched on. A 4K master delivered to a phone wastes bandwidth and storage; a 480p clip shown on a large television looks soft. Picking the right tier is most of the work.
This page gives you the standard tiers plus the pixel maths behind them, so the choice is informed: 3840 × 2160 is 8.3 megapixels per frame, 1920 × 1080 is 2.1, 1280 × 720 is 0.9 and 854 × 480 is 0.4. Each step down removes about two-thirds of the pixels, which is why downscaling has such a large effect on file size.
Features
- Standard tiers from 4K down to 360p, plus square output
- Aspect-ratio-preserving scaling with even-number enforcement
- Pixel-count comparison so the size effect is predictable
- Quality control through CRF in the same pass
- Output to MP4, WebM or MKV
- Works with vertical and square source footage too
Frequently asked questions
Should I convert 4K footage to 1080p?
If the target is a phone, a laptop screen or a web page, yes — the file becomes roughly a quarter of the size with little visible difference at normal viewing distance. Keep the 4K master if you might re-edit later.
Does downscaling then upscaling lose quality?
Yes, permanently. Each resize interpolates the picture, and the detail lost on the way down cannot be recovered on the way up. Always resize once, to the final size.
Why must the dimensions be even numbers?
H.264 encodes in 16 × 16 macroblocks and chroma subsampling halves the resolution in each direction, so odd dimensions cannot be represented correctly. Odd widths are the most common cause of a failed encode.
Can I convert vertical video for social platforms?
Yes — choose an exact size such as 1080 × 1920, or use the aspect ratio calculator to work out the matching dimensions for any ratio.