Common size limits (October 2026)
| Where you're sending it | Limit | Note |
|---|---|---|
| Discord (free account) | 10 MB per file | Nitro and server boosts raise it |
| WhatsApp (sent as video) | 16 MB | WhatsApp re-compresses it further |
| WhatsApp (sent as document) | 2 GB | Keeps quality, no inline preview |
| Gmail attachment | 25 MB | Larger files become a Drive link |
| Outlook.com attachment | 20 MB | Treat 20 MB as the safe limit |
Apps change these limits from time to time. Aim a little under the limit - for example 9 MB for a 10 MB cap - so the file always fits.
Work out the bitrate for your target size
File size is simply bitrate × length. Enter your target and the video length, and the calculator gives the video bitrate to use:
Very short targets for long videos need a lower resolution too. Below roughly 1,000 kbps, scale 1080p down to 720p; below about 500 kbps, 480p will look cleaner than a starved 1080p.
Compress to that size in Fast Video Compressor
- Drop the video into Fast Video Compressor.
- For a rough target, pick Smallest File and watch the Estimated Output - adjust the Quality Level slider until it's under your limit.
- For an exact target, turn on Manual Bitrate and enter the bitrate from the calculator.
- If the bitrate is very low, choose a lower Resolution in Encoding Options.
- Use Compare Original vs Compressed Output to check it still looks right, then click Start Compression.
Shrinking a GB-sized video to MB
Big files are usually big because of a high bitrate, not the resolution. A 2 GB screen recording or phone video can often drop to a fraction of its size on the Balanced preset with little visible change. In our test, a 4K clip went from 143 MB to 65 MB and stayed 4K.
Because everything runs offline there's no upload step. The free edition takes MP4s up to 2 GB; Pro removes the limit. More on compressing MP4 files →
Frequently asked questions
How do I compress a video to 10 MB for Discord?
Use the calculator with a 9 MB target and your video's length, then enter that bitrate under Manual Bitrate in Fast Video Compressor. For clips longer than about a minute, also choose a lower resolution in Encoding Options.
How much room should I leave below a size limit?
Aim for about 90% of the limit: 9 MB for a 10 MB limit, 15 MB for 16 MB. For email, aim for about 18 MB, because attachments grow slightly when they are sent.
Does the calculator account for audio?
Yes. Pick your audio bitrate (128 kbps is typical) and the calculator subtracts it, plus a small margin for the MP4 file itself. The number it shows is the video bitrate to enter.
Why is my video still too big after compressing?
Long videos need a lower bitrate to reach small targets. Lower the resolution or trim the video, and make sure the source wasn't already heavily compressed.
Try it on your own video
Fast Video Compressor is free on the Microsoft Store. Nothing is uploaded, and you see the new size before you compress.
Download free for Windows