What bitrate fits under 300 MB?
Length and bitrate in, file size out — or the size you must stay under in, the bitrate and the ffmpeg command out.
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kbps. AAC at 128 kbps is what Instagram's spec lists 1.
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12 seconds · a made-up example
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How it works
Short and checkable: every limit links to the platform's own page, read on 28 Oct 2026.
Size is bitrate × time
A video's size is its video and audio bitrates added up, times its length, divided by 8 for bytes. A one-minute video at 8 Mbps with 128 kbps sound is about 61 MB.
Aim under the cap
Going the other way, the calculator keeps 2 % for the container and gives the video bitrate that lands under your size. Instagram's API takes 300 MB and 25 Mbps at most; TikTok's 4 GB; YouTube 256 GB.
Two passes to hit the size
ffmpeg's two-pass mode reads the video once to plan, then encodes at the average bitrate you set — the reliable way to land on a size. The command is ready to copy.
What it doesn't do
- A real file lands within a few percent of the number: the encoder and the container add or save a little.
- It doesn't judge quality: the same bitrate looks better on a calm talking head than on fast motion.
- There is no file here, only numbers.
Questions
How do I calculate a video's file size?
Size = (video bitrate + audio bitrate) × length ÷ 8. A 60-second video at 10 Mbps plus 128 kbps of sound is about 76 MB.
What bitrate keeps a Reel under 300 MB?
For a 3-minute Reel, about 13 Mbps in total, sound included, with a little room kept for the file's own overhead. The tool works out the number for any length and cap.
What are the upload limits?
Instagram Reels: 300 MB through the API. TikTok: 4 GB. YouTube: 256 GB or 12 hours.
Sources
- 1Meta for Developers — Instagram API — IG User Media, Reel specifications and captionAPI v26.0 · read 28 Oct 2026
- 2TikTok for Developers — Content Posting API — media transfer guideupdated 4 Aug 2026 · read 28 Oct 2026
- 3YouTube Help — Upload limits: 256 GB or 12 hoursover 15 min needs a verified account · read 28 Oct 2026
More free tools
All 25 tools- Make the videoShort video analyzerWhy does this short work?
- Make the videoScript timerHow long will this script run?
- Make the videoAuto subtitlesNo subtitles yet? Make them here.
- Make the videoVideo to textNeed the words of a video as text?
- Make the videoBurn subtitlesSubtitles that stay on TikTok and Reels?
- Make the videoSubtitle checkerCan people read your subtitles in time?
Rendered to spec, posted for you.
Vertiscale renders every video as H.264 with AAC sound and publishes it to each of your accounts through the official APIs. Publishing is in beta: TikTok posts stay private until our app passes TikTok's review.