SizeFitHow to send a video by Gmail (and why 25 MB really means ~18 MB)
Gmail lets you attach up to 25 MB per email. Anything bigger is turned into a Google Drive link. So why does a 21 MB video still get bounced into Drive?
The hidden overhead: email encoding
Email was designed for text, so attachments are converted to Base64 before they’re sent. Base64 turns every 3 bytes into 4 characters — about 33% bigger — and line breaks and message headers add a little more. The 25 MB limit applies to that encoded message, not to the file on your Mac.
Rule of thumb: to send by Gmail, your video should be about 18 MB or smaller. That’s the target SizeFit’s Gmail preset uses (25 MB × 0.72).
Option 1: send a Google Drive link
If the recipient is happy to download from Drive, a link keeps your original quality and has no 25 MB limit. The downsides: the video isn’t attached, sharing permissions must be right, and some schools and companies block Drive.
Option 2: compress the video to ~18 MB
File size is simply bitrate × duration. To fit 18 MB, the total bitrate (video + audio) has to be roughly:
bitrate (kbps) ≈ 18 × 8000 ÷ duration in seconds
| Video length | Total bitrate | What usually looks good |
|---|---|---|
| 30 seconds | 4,800 kbps | 1080p |
| 1 minute | 2,400 kbps | 1080p (calm footage) or 720p |
| 2 minutes | 1,200 kbps | 720p |
| 3 minutes | 800 kbps | 720p for talking heads, 480p for busy footage |
| 5 minutes | 480 kbps | 480p |
| 10 minutes | 240 kbps | Too little — trim, split, or use a Drive link |
Remember to leave room for sound: AAC audio at 96–128 kbps keeps speech and music clear. Removing the audio to save space is almost never what you want — and some compressor apps do it without asking.
Free ways to do it on a Mac
- QuickTime Player → File → Export As → 720p or 480p. Free and simple, but you can’t choose a size — check the result and try a lower resolution if it’s still too big.
- Finder → right-click the video → Services (or Quick Actions) → Encode Selected Video Files. Same idea: resolution presets, no size target.
- HandBrake (free, open source) → Video tab → Avg Bitrate. Use the table above, subtract the audio bitrate, and enable 2-pass for more accurate sizes.
- SizeFit → pick the Gmail preset. It calculates the bitrate, re-encodes automatically if the result is over, and checks the output before you send it. The free version has no watermark.
Before you hit send: check the file
Whatever tool you use, open the compressed file and confirm three things: it plays all the way to the end, the sound is still there, and Finder shows it under 18 MB. SizeFit does this automatically and shows the results on a verification slip — including whether the audio is present and not silent.
FAQ
What’s Gmail’s limit for receiving?
Gmail can receive messages up to 50 MB, but the sender’s provider may have a lower limit — 25 MB is the safe number when sending from Gmail.
Can I compress a video for Gmail without losing quality?
Short clips usually look nearly identical at 18 MB. For longer videos some detail is always lost; lowering the resolution looks better than squeezing 1080p into too few bits.
Is it the same for Outlook?
Outlook’s default limit is 20 MB, also measured after encoding, so aim for about 14 MB. See all email and chat size limits.
Fit any video under Gmail’s limit — and know it works
SizeFit aims for the real 18 MB target, then decodes the whole file to confirm it plays to the end and still has its audio.