Gmail says 25 MB, but attachments are base64 encoded in transit, so the real ceiling is closer to 18 MB. This targets the number that actually gets through — compressed in your browser, never uploaded.
Quick answer: Open the Convertlo video compressor set to 18 MB and press Compress to size. Gmail's stated limit is 25 MB and Outlook.com's is 20 MB, but email encoding inflates a file by about a third — so 18 MB is the size that reliably arrives. The tool measures its own output and re-encodes if it landed over.
Compress your clip for email Nothing uploaded · no watermark · no signup
This is the part that catches people out. Email attachments are base64 encoded before they are sent, which makes them about a third larger in transit. Gmail's 25 MB applies to that encoded message, so the real ceiling for a single file is closer to 18 MB. Aim at the stated limit and a file that looks like it should fit gets bounced.
Provider
Stated limit
Realistic file size
Gmail
25 MB
~18 MB
Outlook.com
20 MB
~14 MB
Safe for anywhere
—
18 MB or less
The recipient's server also gets a say. Their limit can be lower than yours, and you find out by bounce, so the smaller number is worth taking seriously on anything important.
How much video fits in 18 MB
Worked out from the bitrate budget the compressor actually uses. "Looks good" holds up on ordinary footage; "still watchable" goes soft on fast motion.
Resolution
Looks good up to
Still watchable up to
1080p
43 sec
1:11
720p
1:33
2:28
480p
3:11
4:46
If your clip is longer than these, drop a resolution step rather than accepting a smeared 1080p. An email attachment is almost always watched in a small window, and 720p at a healthy bitrate looks better than 1080p starved of one.
Pick 720p or 480p if the estimate says 18 MB is not reachable at full size.
Compress, download, attach. The output is verified to be under the target before you get it.
Sending to a specific provider with a different cap? Type any number you like into the exact-size box — 14 MB covers Outlook.com comfortably.
Frequently Asked Questions
Gmail is 25 MB per message and Outlook.com is 20 MB. Other providers vary, and the receiving server has its own limit too — a message can be accepted by your provider and bounced by theirs. 18 MB is the size that gets through essentially everywhere.
Because the limit applies to the encoded message, not the file on your disk. Email attachments are base64 encoded, which inflates them by roughly a third, so a 24 MB video becomes about 32 MB in transit and is rejected. Divide the stated limit by about 1.37 for the real ceiling: 25 MB becomes roughly 18 MB of actual file.
About 43 seconds at 1080p, 1 minute 33 at 720p, or 3 minutes 11 at 480p before quality starts to suffer. For anything longer, 720p or 480p is the honest choice — nobody watches an email attachment full screen.
For anything over a few minutes, yes — Gmail offers a Drive link automatically once you cross the limit, and that avoids the whole problem. Compressing is the better answer when you want the file to actually arrive in the message, for example for an attachment that has to be archived with the email.
No. It is encoded in your browser by your device's own video encoder, so the file never leaves your machine. That matters more than usual for anything you were going to email in the first place.